How to Segment Customers before Building Product?

Hello IndieHacker Community,

A friend and I are working on building an e-commerce tool based off of a problem a few sellers told us about. We're trying to segment our potential users to see how big and painful this problem is for different e-commerce sellers, but we're having a hard time finding sellers to interview. I come from a heavy UX background and I always like to make product decisions based on customer interviews. I've tried going to e-Commerce meetups and Reddit, but it's difficult to get people to respond. What strategies have you guys used? Should I just forgo ux research and just ship my product hoping it will stick?