It seems this is same question has been asked since the early 2000s in this forum with no resolution. I wish shopify reviewed these pages and found solutions for what customers are looking to do. I would like to have the ability to add two items on one page as shown below. Does anyone know how to do this? The apps i've seen dont look very appealing to me. Any help is appreciated.
This is a solution that involves, as per your example, some custom work. Technically what you see here are 3 separate products and it most likely works by using two separate templates. The first one is a mock product, which you cannot buy, but it includes two real products (top & bottom), which are what gets added to the cart if you select them. This can be achieved using a variety of methods, most common of which is one type or another of a JS library and some coding. A Shopify developer shouldn't have any issue with providing you with a solution.
Unfortunately, I don't have any recommendations for an app, haven't used any for this kind of feature.