Build an Online Store

I need some one who can design an online store for T-shirt sales. I need to be able to offer customers the option to customize shirts they would like to order. Now here's the catch I also want the ability for the T-Shirts that are actually being sold to be a group buy. Say I need 20 people to buy a certain shirt before it can officially be order. If it doesn't reach the target quantity then no one is charged and the T-Shirt is not processed. I can provide a website that is set up the way I want my web store set up in order to show you what I am talking about. I have created websites before and have a general idea how to build them but trying to figure out how to build this site the way I want it is already been time consuming and I need this site up and functional ASAP!! Please let me know if you think you can pull this off and how soon. I will be more than happy to provide more information.