Gary haugly former owner of B&R buggies does this for a living, including classic cars and hot rods. He works at prp seats and u can probably find his contact info on Facebook or social media. That's my recommendation.
Incase either of those guys can not do it. I used Pinnacle auto appraisers (877-988-9911) https://www.autoappraisers.com/. Sent a bunch of pictures and gave specs, paid a fee. They produced a report that the insurance company was happy with to get insurance on buggy.