You might contact Harrett Stocks and see if they make them.
Looks like the only "Roper" they have on their website is for revolvers though.
I cannot find any pictures of Ropers for bullseye shooting, so I'm guessing they are more of a classic bullseye grip.
Just a suggestion, but a lot of things have changed since such stocks were first introduced all those years ago. Why not instead get a modern European style wrap-around grip for the M1911?
Such as the Vitarbo:
There are probably two or three other makers of similar grips. My wadcutter gun wears Morinis and they just blow old-fashioned grip panels clean out of the water.