Configuring Boost Sales

I was going through your knowledgebase and am still confused on how to do what I want.

I want the following:

When someone purchases a pair of sunglasses or a visor from my store. Lets say its 29.99.
I want them to have the option to add a lens cleaner for 3.99 (usually a 5.99) product.

Is this possible? I tried changing the price in the bundle product area but it was confusing at checkout. It changed the price but never added the lens cleaner as an item on checkout. This would be confusing to customers as it doesnt really tell you if its in the cart or not.