Fiverr is one of the biggest providers in the gig economy on the web and you can sell a wide variety of services and products through this medium. Do the research and find out what you can offer. However, keep in mind that like any other money-making task, it takes time to succeed here. And stellar reviews will help you generate more and more income over time.
Contact the company directly. If you use a product or service and want to recommend it but you can’t find evidence of an affiliate program, consider approaching them and asking if they are willing to set one up (maybe with your help). Highlight your audience and the value of your recommendation. Explain that an affiliate program is simply rewarding happy customers (you!) for promoting, and they don’t have to pay until a sale is made.
If my piece of content is so unique and valuable around hiking backpack recommendations, that other reputable outdoor websites are willing to link to it and build the page’s authority, then I’d have a very real opportunity to rank high in organic search for these search terms (meaning, my page will come up first when someone searches for hiking backpacks).