If you search for “pokemon anime cel” you’ll usually find a bunch of the original anime art cel frames for sale on eBay and alike. I currently see thirteen for sale, but prices vary between 375-5000 USD for those.
There was a very brief thread about them a couple of months ago: www.elitefourum.com/t/animation-cel-collectors/27527/1
Without that I wouldn’t even have known about the term ‘cel’ to be completely honest (English isn’t my native language).
Greetz,
Quuador