Optional Add-ons In Quotes for Upselling

I'd love to have the ability to offer my customers add-on products when they are reviewing their quote. We have used other programs in the past that had this capability and it was very successful in increasing sales. For example, they are buying t-shirts, and I can add a line for a laser engraved tumbler at a discounted rate. If they want it, they click on it and it adds it to the quote.