Rather than hit the common spots for scripts and the "same old stuff" you may find the suggestions below worthwhile.
Take a look at some of these to see if you can "compromise" enough to make them work for you.

Top-of-the-line system, http://www.phpshoppy.com/products/ho...vation-system/ , but $235

FREEBIES (check out the features of each):
http://www.bigwebmaster.com/1596.html

http://www.getfreesofts.com/script/2...ng_System.html

http://online-sales-software.qarchive.org/

(a selection, actually, from a favorite source of trusted tools) http://online-sales-software.qarchive.org/


Find freelance programming for any budget or project here (if you want to tweak something that looks promising): www.odesk.com