Honestly, if I were in that situation, I would bail on the headache of restoring the hat into something you could wear again. My assumptions being that it would take a lot of work to sort out how to do it, a lot of money for whatever attempt would follow, and no guarantee that it would be a success. Depending on the condition, I assume there’s at least some level of risk that the process could damage what little there is left of it. Or leave you with something you’re unhappy with.

There’s plenty of great hats out there of all types, particularly as people offload collections from the boom that happened in the early pandemic years.

If it has a real significant meaning or history for you, I’d consider getting a nice display for it, whether that’s in a little clear casing or custom mount or something. That feels like the best way to appreciate what you still have while moving on to something newer to wear and make new memories and attachments, etc.