Creating quote/proposal

Site URL: https://tommy-brown-kgtg.squarespace.com

I'm helping a friend build a Squarespace site for his business. We would like to build a products page where the user can select the things they think they need, then my friend receives that list to verify they have everything before approving the purchase. Basically, I want the end user to build their own quote, then get approval from the site owner.

Suggestions on how to accomplish this?

Thanks in advance!