Ricoh GR already has GW-3 wide adapter that is properly designed for the GR.
So I can see why no one bothers to try a wide adapter from 3rd party or another company.
Do note that you will need the GH-3 adapter to screw on the GW-3.
In theory, as long as the wide adapter lens screw filter diameter is the same (on the mounting side), it will fit.
I have tried the GW-3 on the Sigma DP1m too.
But as it was not optically designed for DP1m, the edges were not to my requirements.