It might not be OEM, but Williams or Marbles will likely have an appropriate replacement.
OTOH, I doubt Marlin was in the sight making business & likely bought from one of the above or similar.
Fwiw, it won't be the first time new owners of a defunct company can't or won't support the firearms made under the last makers.
And BTW, I ordered a Marbles a few months ago & it was a very nice unit. I had 3 or 4 blade choices & 2 choices of over all lengths. Reasonable cost as well. IIRC, Midwest Gun Works was my Marbles source.
OTOH, I doubt Marlin was in the sight making business & likely bought from one of the above or similar.
Fwiw, it won't be the first time new owners of a defunct company can't or won't support the firearms made under the last makers.
And BTW, I ordered a Marbles a few months ago & it was a very nice unit. I had 3 or 4 blade choices & 2 choices of over all lengths. Reasonable cost as well. IIRC, Midwest Gun Works was my Marbles source.