custom price from email, add to cart?

A product has a set price and we offer "customize this product", by using the "Ask a question" contribution, we email them back with an additional price.

How can they add the additional price to the order in the ordering process?

Example:
Customer wants this product but with a different colored shirt and writing on it.

So, the customer hits "Customize this product" sidebox link and we respond back with the additional cost of $20.00 to the original price of $89.00

Here is a product page from the site

Can you use TEXT attributes for this? If filled in charge them the $20 if not, don't charge them?

... or indeed, a radio button or dropdown menu with each selection having an associated price. (Customization level 1 - $20; Customization level 2 - $30, etc.) You'd have to decide in advance on a fixed menu of choices, but it's the easiest way to handle this.

Good luck,
Scott

That is what I was thinking with Attributes, but was hopeing that there was an easier way.

Thank you for your help! I'll test both ways.