Here's what Squadron has to offer. Other on-line stores may have more, if none of these interest you.
http://www.squadron.com/SearchResults.asp?ScaleList=48&TypeList=15&ManuList=everything&Key=P-38&Submit=Go
Here is what Aeromaster has:
http://www.eaglestrikeproductions.com/cgi-bin/amd2.pl
(just select P-38 from drop-down menu)
And here's one more list:
http://m2reviews.cnsi.net/decals/decalsor.htm
Hope this helps.