Costco is a big box warehouse store like Sams Club - don't know what they have out there by you Karin. Costco is the best of the best for warehouse buying! We buy so much stuff there.
If the Costco option does not work, then your local bank will be able to help. Just go in and tell them that you want to set up a business account and that you want to be able to take credit cards.
I am off to a show in Monument, CO tomorrow - a 4th of July street fair. I will be just selling prints and small originals. I hope I will do well.