to the OP: your rear sight has to match your handguard, the 1892 rear sight and the 1896 rear sight use the same handguard, the 1898 and 1902 rear sight use the same handguard and then the 1901 rear sight uses a hadndguard. All rear sights will fit the barrel but they need the proper handguard and if this is not the question and if this has already been explained, I apologize.

There are plenty of rear sights on ebay and elsewhere for your rifle and they are anywhere from 35 bucks to 100 bucks.