There are some Facebook pages dedicated to fox hunting horses for sale. There actually are many juniors that fox hunt, and there are also petite adults that enjoy hunting on ponies. For juniors, there should be quite a number of them in Virginia, can you connect with a local hunt there?
To sell a fox hunting pony, you would want to be able to list the seasons the pony has hunted and with what hunts. It is helpful if a master at one of those hunts can vouch for the pony.
People may be reluctant to spend good money on a pony that has not hunted consistently over a certain amount of time as some horses/ponies start out great but then start to anticipate or get worked up over time. Also any horse or pony that is being sold as a hunt horse should be actively out in the field hunting as much as possible.
Just to brainstorm, right now some hunts are either doing end of season hunts focused on juniors or holding/getting ready to hold their qualifying hunts for the Junior Field Hunter Championships so there might be more juniors about in the hunt fields right now.
Good luck! Good hunt ponies are worth their weight in gold.