PCs on Sonic Adventure Merch?

[Noxxbunny]

So the boyfriend has been doing closet and garage cleaning and he has a good amount of old Sonic stuff from the Adventure era. And even more shockingly, most of it is MIB! So I want to help him get some decent prices for his stuff since I'm aware that some of his merch is relatively valuable. And it's certainly ALL too valuable to throw in a garage sale. So he's left the PCs to the collector here lol.

So what he's got so far;

A Sonic Adventure Bop Bag(It's a punching bag that has Sonic on it) it's still in the box
4 sets of Sonic Adventure gel pens. No idea if those still work though...but again, MIB.

And the more interesting ones...

A Big the Cat plush.
And a large Sonic UFO catcher plush
Neutral Chao plush
All still unopened in plastic bags.

He also has some non-SA1 stuff;

He has a full MIB set of the large Sonic X Toy Island figures(Sonic, Tails, and Knuckles)
Some small Sonic Underground plush
A Sonic clock radio(No idea if it still works though...)

Any help is much appreciated. Even if it's just directing me somewhere knowledgeable about this sort of stuff. I couldn't find a Sonic collectors forum or anything. And of course, if there's any interest in actual buying, I'll post a sales thread in the appropriate section. While this is the stuff that I don't know how to price much, he has some other fresh 90s goodies like Pokemon and Digimon related things as well.