Kent,
There is no way to fix them.
It's only a matter of time before the rest die too.

: I have 4 Kohler 81100 Pressure Toilets in my home. One of these systems recently had a failure at the flush valve which flooded the bathroom and bedroom where the toilet is installed. A second unit has a pressure leak at the valve, which is semi contained by the tank cover, but results in low pressure operation. Needless to say, these 2 bathrooms are out of service at this time.

: I understand that the 88100 system is out of production and has considerable risk/history of failure. Consequently, I want to replace all 4 systems at this time.

: Do you know if a modern pressure pump/tank system can be installed in the existing toilet porcelain fixture so that I don't have to replace all of the toilets and matching bidets ?