more website input (desperately) needed

The image above is my current website, which I built myself using iweb. Now I'm using an e-commerce site builder to manage the products in my new shop, and I've run into one tiny problem. I can't have three individual add to cart buttons on each item page. So, I have two options.

Option 1:

Have a landing page for the art prints where you choose which size you want. Each section will have every single print for you to choose from, but if you change your mind about what size you want, you'll have to navigate back to the main Prints page and choose a new size.

Option 2:

A drop down menu where you choose which size you want. The drawback to this option is that you need to select a default size & price. So every print would be priced at $5.00, and you could choose to upgrade to 8x10 or 11x14 for an additional fee. I'm afraid most people wouldn't notice that you could choose a larger size, or would feel mislead by the $5 list price, if I choose this one. (With both options there are individual pages for each item.)

I'm not thrilled about either choice, but ultimately these are my only options. Which would you prefer, and which do you think would make it easier to shop?