Female header should be available from some DCC retailers, or from online electronic supply houses (like Digikey). There was a recent thread with someone looking for a similar connector in this section of the forum (and finding it). You need to measure the spacing between the pins to get the right header.
I looked into the circuit board in the Bachmann tender back in 2008. The circuit board in that tender contains some components which might make your install not as easy as it might seem. Assuming of course that your tender is the same as the one I evaluated.
This is a copy of the write-up I originally posted on the Atlas Forum:
I've seen several questions posted on various forums relating to the new Bachmann tender internal wiring. I decided to document this info and present it to the forums.
While the tender does contain a circuit board it is not a DCC decoder nor it is very useful for hooking up a decoder when used with a non-Bachamann locomotive. While I don't have any new Bachmann steamers which use these new tenders (I only have the tender itself) I assume that the circuit board in the tender is designed specifically to accommodate the "umbilical cable" which electrically connects the tender with a loco. I'm basing my deduction strictly on what I see inside of the tender.
Here is a photo of the tender with the body removed.
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Here the circuit board has been detached from the tender floor to provide the bottom view of the circuitry. Both tender trucks and the draw bar connections are wired to the circuit board using a red and black wire. Per standard wiring practice red wire is the electric pickup from the right track while the black wire is from the left.
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Next is a closeup of the bottom of this circuit board.
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Next photo shows a top closeup of the circuit board. The 6-pin male connector shown on the left is for the "umbilical cable" which connects loco to the tender. That cable carries the positive (M+) and negative (M-) motor connections, positive (L+) and negative (L-) headlight connections and redundant positive (R) and negative (L) track connections. I say that those are redundant because those connections are already made through the tender's draw bar. Also shown is what might possibly be a location where a DCC decoder could be wired (lower right of the circuit board). Those are 8 gold plated solder pads which are currently shown shunted with 2 shunts. The pads are numbered out of sequence 8 1 2 4 5 6 7. Shunts short out pads 8-1-2 ans 4-5-6. This tom me appears to be a configuration designed for DC operation when this tender is used with a Bachmann loco. Those shunts connect the positive and negative motor pins (M+, M-) to the right and left rail pickups (L, R). They also connect (through 2 diodes and a resistor in series) the headlight pins (L+, L-) to the rail pickups.
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When the shunts were to be removed in a tender which is attached to a Bachmann loco using the "umbilical cable" I suspect that those solder pads are used for wiring in a DCC decoder. Here I speculate how a decoder would be wired in a Bachmann locomotive attached to this tender. Note that there is no rear headlight so the yellow decoder wire would be left unconnected. I also do not know the purpose of pad number 7. The way it is wired on the circuit board doesn't make sense to me.
This photo shows possible decoder hookup when this tender is used with a Bachmann loco and connected to it via the "umbilical cable" (with the shunts removed). The decoder wires would be soldered to the pads on the bottom right of this board using the color codes as shown in the picture.
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I traced all the connection on the circuit board and I created a wiring diagram shown here. The chokes (coils) and capacitors are used for RFI noise reduction (for non-US markets). I'm not sure what is the purpose of those two 220K ohm or the 470 ohm resistors. The 1.5K ohm resistor is used as current limiting resistor for the headlight LED. Using 2 diodes in the headlight circuit also seems a bit redundant to me.
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I really don't see any advantage in using this circuit board when the tender is used with a non-Bachmann loco. Since there is no "umbilical cable" this circuit will not really be helpful. Even if someone created their own "Umbilical cable", the extra components on the circuit board would just complicate the wiring. The easiest way to use this tender in DC mode with a non-Bachmann loco is to ignore the circuit board and just use the draw bar connection for tender pickup. For wiring a non-Bachmann loco using a DCC decoder the simplest way would be to discard the circuit board and place decoder in the tender. Then use the draw bar for the track power pickup from the locomotive and run decoder's orange, gray, blue and white wires straight to the loco. Those will power the motor and headlight.
