Discontinued Kubota part

Have a problem with my old model, though it's only done just over 700 hrs, Kubota GL6500S generator. After it's warmed up and with around 25% full load, the voltage is high at around 246 volts and for short periods, jumps to 296 volts ...its a 230 to 240 volt 50Hz unit. I pulled out the Emergency Relay Unit and checked the various resistances (between pins) against those listed in the Yamaha EDL6500S manual (I believe it's the same unit with Yamaha branding). The resistances are mostly quite different from those listed so I'm thinking to replace it. But it's a discontinued item so wondering where I may get one? Is Aftermarket Express a legit supplier? Are there any others?