Help With Bryce Harper's AFL Champ Cap

[Basinballers]

We have Bryce Harper's cap that he wore in the Arizona Fall League Championship game. A friend (who works in the clubhouse) wants to consign this in my eBay store. The big problem here is how do we prove the authenticity? Harper did not sign it for him but did write all over the brim prior to wearing it. I use JSA for my signature authenticity and I asked them to look at it at my last session with them. They took photos but after all was said and done, could not authenticate the writing due to Bryce being a relatively new star and not enough hand-writing to compare yet. So here we are with a great item and no way to market it. Any ideas?