If Jack First doesn't have any, try:
Bob's Gun Parts
http://www.shotgunlife.com/shotguns/...millennia.html , who has the old Marlin FP @ $35;
or
Wisner's
http://www.wisnersinc.com/rifles/marlin/rflever.htm who makes & sells them for $20.50 (part # A39A-32)
.