A replica isn't going to happen on a $100. budget. You might get a no drill no tap add on though.
There are several under $100, but none replicate the original in look or function. They do let you add a scope but in ways different from the screw in pads of the original system.
B-Square makes one for about $50 (although I don't care for it's quality). There are a couple of others that use the rear sight axis pin & charger bridge that work fairly wel, Do a quick google & you'll find them easily.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”