I've used a stove top pressure canner (a small 12 quart one) to help make invert sugar and regulate the temperature.
I start the sugar, water, and acid on a normal pot on the stove to get up the syrup to 240 degrees. I then transferred the invert syrup into pint mason jars (which has ended up being about a pound a piece), add those to the canner, and let the pressure canner come up to pressure and ~250 degrees. It's easy to keep it there for anywhere from 20 minutes to a couple of hours depending on which grade I'm making. It worked pretty well and gives me nicely portioned amounts in sealed containers. I may make a bunch of cup jars next time for extra flexibility.
I've also made small batches of invert #1 this way when I've also needed to can some wort for yeast starters. Increase the pressure time to whatever you need and you get some sterilized wort and lighter invert sugar at the same time.