Hi, we have developed the similar products therefore it will not very difficult to customize shopping cart to fit your needs.
So, we offer shopping cart (Perl + MySQL) with admin area (products maintenance, title, descripiton, picture, 2 prices as required, category if need this), buyers area, email messages as order confirmation and integration with payment gateway. I wonder if you already have members access area or some kind of members login script, if not will add ours.