Took a few minutes this evening and threw together the first of 2 Showcase Miniatures Propane trucks. Hoping to find some Suburban decals for them. I have Amerigas ones somewhere
If this is what you are looking for:
or this:
and have a color printer, then you should be easily able to roll your own.
It appears to be the very popular Helvetica Black Italic font (or one of the many clones of it). You should be able to create the artwork in any graphic programs (or even MS Word). Since the decal will be applied to a white model, no need for white undercoat. Just get some decal paper, print, seal (if printed on ink jet), and apply to the model.