they are not available any more.
I had 3 of them, stashed. Gave them all 3 away to a guy who buys a bunch of equipment. He said they have no value unless someone wants a grass catcher on a G1700/G1800/G1900/G2000. Grass catchers were a rage 30 years ago, not so much now. The society has become one of convenience and a mulching kit trumps a grass catcher in that sense. The only people who might want one would be a lawn care service, and 99.99% of those are using zero turn mowers and/or walkers with built-in catcher, for the 2 yards of their entire workload that wants the clippings picked up.
only way I can see any value in them is if you were to sell a G1800/G1900/G1700/G2000 (compatible with your catcher), WITH the bagger on it. It might bring $100 more than one without, but you gotta find that one person who wants a bagger system. They are a pain. More specifically disposing of the clippings is the worst part.