Ecommerce to Wordpress existing site

I have an existing website at http://www.chutepartsonline.com. I want to keep this exact format for SEO reasons. I just need somebody to integrate a purchase button and a checkout with a shopping cart. I want the checkout process to be very fast. It should allow the calculation of a shipping cost based on weight. All I really need is way to create a purchase button that I can connect to the checkout process. I have [login to view URL] as a checkout process for another website. I want to collect the credit card information and Items and cost on this website, and then with that information, I will manually process the credit card on my own using the [login to view URL] control panel I currently have. I just need a button creator for each product, and a checkout process for the information to come to me so I can manually process the order. I'm looking for an affordable way to do this. Good luck with your bidding.