(this post is a feed post from my comments on reddit)
r/startups
Companies that do this exist for corporates with budgets, neilsons for example will take a brands products and do both quant and qual research for the brand that costs a fair chunk of change.
The paradox you’ll encounter with startups is
1. They have no money
2. (Opinion) the founders should be doing these interviews themselves so they get the feedback first hand.