The Model 1000 was slightly early for the synthetic stock days.
As far as I know, neither S&W or Mossberg ever made a synthetic stock for it.

Possibly Choate did, so I'd email them and ask.

Last NO GUARANTEES, but it's possible a stock made for a Remington 1100 might fit or could be altered to fit.
The 1000 was NOT a close copy of the Remington 1100 as some people think, but it's possible the stocks are close enough.
This is something that Choate might well know.