Motosens sells adapters for their gauges. You might find the info you are looking for there.
If you speak German that's the way to go if they still stock the right parts. I can't remember whom, but a couple of years ago someone tried to order stuff from them after the company changed hands, and they had to put in a fair bit of effort just to communicate with them.
I don't think an oil pressure gauge is needed, as oil pressure has never been an issue for Valkyries. I installed a coolant temperature gauge from Autometer, and drilled and tapped the unused boss on the thermostat housing to use their temperature sender.
