Earlier this year, it appeared that R$F stocks at least some replacement input shaft kits.
The 8.9:1 and the 10.35:1 use the same input shaft which has a 27-tooth helix gear.
The 12.44:1 uses an input shaft that has a 21-tooth gear.
You’'ll probably have to contact them for the kit. And, be advised that dealing with Bob and his Oompa-Loompas is often somewhat the opposite experience of working with the staff at NEV-Accessories…