I couldn't find any vinyl, Lettraset or similar numbers available in the correct font so I did a bit of research in the books and drew up 0 to 9 (and 'PT' for those that insist on putting it on their models) in a common font for a late war Elco PT's, It's not quite correct for early boats like PT109 etc, but hey, I'm not building one of those!
The sizes and proportions are from a close up photo of the numbers on PT305 (The Higgins) but are styled more in line with the fonts used on the late Elco boats.
On the sheet below I have scaled the numbers to be 30mm and 15mm for a 1/16 scale model and 24mm and 12mm for 1/20th scale. The large numbers go on the hull and the 'half' size smaller numbers go on the superstructure.
I am proposing to get these made as an A4 sheet, so if you are interested I can post you a set for a small fee, if you e-mail me at info@pt-boat.com I will contact you and make arrangements.!