You could consider getting one of the decal printers to make some up for you (
Griffon Games and
Ginfritter's comes to mind). If you can't make them yourself in vector-format the labour cost could be a bit high though... The upside is that if you're artistically inclined vectors aren't really all that hard to work with, even I can do it
The other option is getting some decal paper for printers and just print them yourself. The quality might be lower but it's quite a lot cheaper. Just make sure you get the right kind, either for laser or for inkjet printers.
To weather decals just put them on, paint on some clear enamel, and then weather away
