Check here:
ht tp://thegreatmodel8.remingtonsociety.com/
or here:
ht tp://vintagesemiautorifle.proboards.com/index.cgi?
As Jim mentioned, they have fixed magazines UNLESS yours has a conversion kit put in and the mag got lost. There were large capacity mags for the prison guards and police in the US but they were for the 35Rem from what I understand.(That ain't much)!
The boys on those two forums will be able to help you if you post pics to confirm what you are missing.