There are thousands of quality merchants waiting to be your partner. You could contact them separately. Or you could work with a company that represents thousands of merchants. One of those is:
You do not need to create your own product or service. In fact, merchants as diverse as those shown below are willing to partner with you:
When you click on one of the links and make a purchase, the merchant credits the forwarding website - and if it is your site, you make a commission!
Of course, Internet merchants such as eBay and Amazon have similar programs. Amazon has some very complete "stores that you can incorporate into your site.