Aftermarket voltage regulators for 912iS?

You may be playing with fire here if you get the wrong reg/rec or hook it up wrong and cause damage to your pocketbook. Why not leave it as the factory has tested.

I'm not worried about damage to my pocketbook and I'm happy to pay a professional to do it.

My mission is one where I may be using very little electric power so for the majority of engine operation, regulator B will be nothing more than a 400W heating element. It would be nice to be able to avoid that and have a regulator that works like the ones in nearly every other aircraft engine.

Two suggestions. First you can install the optional heat sink from Rotax SI-PAC-019.

Second, if money is no object then run a portable AC unit when it's hot. That way you use those extra watts to keep yourself cool! ?

https://www.sportys.com/arctic-air-portable-air-conditioner-38-qt-single-fan-12-volt.html

I was considering HID lamps to use up those wasted watts and improve day visibility where weak LEDs are almost useless. Sadly that "AC" you linked isn't real air conditioning and is just an ice box with a fan. Real AC takes a little more than a 400W generator can provide. They usually need a dedicated aux generator.

Joe

The easy way to consume energy is simply have some landing lights that you power in flight.  On the B side you have 30 amps to power the aircraft.  In normal configuration calculate what you use from all your electrical load and then add on some old fashioned lights rather than LED if that is what your aircraft has now.  The suggestion for the optional heat sink is a good one and be sure that you have air flow to the heat sink to cool that part regardless.  Some aircraft are good in that way and some lack enough cooling to the regulator mount.  

I am aware of a few people who even remote mount the B regulator to get it into a spot where it has adequate cooling.  Might be an idea if you are having problems with it as long as it is experimental that should be easy. 

Cheers