While the 6100 will work with 128 MB SIMMs, the 7100 and 8100 will not.  The logic board runs the upper address signal and the RAS select lines through a CPLD, which apparently expands the number of SIMM sockets at the expense of SIMM module capacity.   In brief, the 7100 and 8100 won't address more than 16MB in a bank, so a two bank, 32 MB SIMM is the largest supported.

I've post some HP and Samsung part numbers for 128MB SIMMs which are good search terms.  The Advanced Search feature should turn them up.  The postings are few years old.