CAN bus with CANL only?
I've just discovered that there are heaps of CAN transceivers that operate at 3V3, and thus have a 1.9V recessive voltage (yes, they can only speak to other CAN devices that operate at 3V3). This solves the levels part of my question, I'll use the tip provided by @'Tony Stewart Sunnyskyguy EE75' to try and hold CANH steady and see where I land.

Thanks!