I've added services to my website for creating and providing custom decals. Much like the WW2 sets offered on my other site Company B, but for Sci-Fi themes and specifically for small ships. All scales can be created, 6mm to 1/35.
All decals are created as vector graphics. Can be from existing sources (cheaper) or completely custom designs (a little more $)
Samples below from custom requests and currently available sets:
https://littlemetalspaceships.com/pages/custom-decals