Not familiar with the particular machine and find this--if you are being told correctly the part is not replaceable--reprehensible on the part of Kubota.
Can you access from the (assumed from the post, plywood) bottom?
The switch itself won't be--shouldn't be and almost certainly isn't--unique to that machine.
Try online electronics houses (Mouser's comes to mind--free paper catalog too; McMaster, Grainger) for a replacement switch. Examine the switch for manufacturer and part number and an OEM replacement should be readily available.
Replacement might require whittling or using RTV or a wad of duct-seal or something equally imaginative.
Seat safety switch is important, but depending on who the user(s) is / are (kids?) and cost of a new seat, you could elect to retain the bypass.
Understand this--bypassing the switch--negates completely any recovery by your surviving spouse in case of fatality or damage to your person.
I have rigged a safety swich by wiring a female stereo socket into a circuit and then tethering the male stereo plug (with internal connectors shorted together) to my person with short leash. Plug in when seated runs, stand up leash pulls plug, shuts down. Tie to belt loop with caribiner or thumb-clip. Any similar device would work and may be able to find something commerically available that does the same thing. Less idiot-proof than seat switch as requires positive action on part of user but perhaps better than nothing.
Please post back your continuing experiences so we may all learn.
/s/Lucky Nine Toes
