Yes Marble still has a peep sight. they call it a tang peep sight.
They are in Michigans Upper on the shores of Little Bay De Noc, have been since the mid 1800's.
Check out their web site and look at the tang peep sight.
http://www.marblearms.com/index1.html
You might also want to look at what Williams has to offer.
http://www.williamsgunsight.com/
1340
FP-Hawken
For pre-1991 Thompson/Center Hawken and Renegade M/L rifles. This sight fitted with sub-block. It is necessary to drill and tap one hole on models that factory discontinued drilling.

Al