Toto TWT173M 1.28 GPF Dual Flush In-Wall Toilet Tank Only with Copper Supply Line

I have a toto in-wall carrier and wanted to add atoto washlet. Lots of issues!1. No where in the instructions, for the washer or the tank does it tell you that you need their PROPRIETARY shut-off valve. After the plumbers messed around with it for several hours and a couple of trips to a specialty plumbing store with no luck, I called toto and was told of the mystery, necessary part.2. Poor customer service as the rep was very condescending and making excuses for why it isn't in the kit or instructios.3. The PROPRIETARY chrome shut-off valve in question is $160.00! Yes, because charging 3 times what everyone else charges for these systems isn't enough. There is absolutely no reason, other than to rip you off, does this part need to be proprietary.