Idea replies — I have human-centered design (HCD) experience for web and digital products and a few free hours a week

What about specializing in abandoned checkout processes? Small online businesses often spend money attracting visitors but have no idea how many customers give up because their checkout is confusing. You could review the process, identify unnecessary steps and show owners where they're losing potential sales. The commercial benefit would be fairly easy to explain, and you could build a nice collection of before-and-after examples.