No idea as to the switches, but ther service manual for the 808 is here Audio Roland : Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics
The manual for the 606 is also there
Clone information for drum circuits from the TR808 is here
eric archer . net » 808 clones if you want to build a triggerable sound module for each drum sound.
I know its not what you are after, but maybe someone is interested.....