Have you talked to your printer? They would be the ones most able to do what you want. It's not unusual for printers to inventory merchandise for their customers. Heck, it got to the point with my printer that my orders were coming in to them so regular, that if I ordered 500 shirts, he would print 1,000 or more to get that next price break. He would inventory the other 500, and bam, when my next order came to him, they were already ready. Of course, he did not pass on the savings he realized

. Carrying costs, I guess.
But I would certainly start there. Consider:
1. He already knows how to print your shirts. He's doing it now.
2. You know he can supply the shirts you like.
3. You know he can do it within the $16-$20 retail range.
4. You know he can handle shipping. He ships every day.
5. He already knows how anal you are.