Try
www.champ-sys.com
Full color, dye sublimated jerseys
Minimum order is low, 10 I think. $45 each. Check out there gallery and you'll get an idea of their work. I'm getting ready to order from them, and they've been great to work with so far.
About sponsorship. I don't race, but someone out there might be able to answer this. If you get corporate sponsors, does that monkey with your amatuer status if you ever want to race in sanctioned events?