High rise toilet

Are there any RV dealers near you, that were Roadtrek dealers before the Hymer take over? Maybe someone at one of them can tell you, if they still have service staff from way back then.
Or, you could measure the base of what you have and ask at an RV parts shop.

They make riser kits. They also make hi-rise toilets.

Aqua-Magic Residence RV toilet / High Profile / White - Thetford 42169 Is one model. They are avl on Amazon for $179.

https://rvlife.com/techtips-installing-a-toilet-riser/

Thank you for the information. I found a Ada toilet