Selling Custom Shells

I'm an artist, and I've been wondering: if I wanted to start selling console shells with my own artwork screenprinted or UV-printed on them, how would I go about that? I see people selling them all the time, but I don't know what services they use to have them printed, and I question the legality of sourcing shells elsewhere and then reselling them once they're printed. I've used a store that offered UV printing service for their shells to have my own artwork printed on one, but only a one-off for personal use. Anyone have any experience?