There are a few people that make them for small diesels but none are internal like your looking for.(BD, Banks, and Pacbrake that I can think of off the top of my head) Banks is the closest one and it's on the back of the turbo IIRC. Pac Brake bolts on at the flange between the front and rear pipe by the tranny. They all work basicly the same, just cut off exhaust flow. They would almost have to build just as much heat as an internal in my opinion by pugging the pipe off.
All run around $1000-1500 last time I checked.
Ok not to start a fight about them, but here are my thoughts on Jakes causing heat problems.
I've heard a lot of people say that they are hard on a motor, but never any proof so mine stays on. It was hard on them back in the day when people were turning them on and then putting the accelerator pedal to the floor because the extra fuel made the jake work better, that's what caused all the heat and burnt them up. The only way they will stay on anymore is with the foot off the pedal, and the engine in DFCO mode and there is no way it can build up more heat with no fuel then pulling a load up a steep slope.
Why if they are so hard on them are they on almost every truck on the road? Those things are lasting millions of miles and most drivers do like I do. My jake switch stays on ALL the time, now that I think of it I don't remember the last time it was turned off.
It's on an end dump hauling into and out of const. sites all over Kansas City so it gets used plenty. Trucking has been my families business for several generations and since electric cutoffs were put on the pedals I've never even heard of a jake brake heat issue causing problems. I'll never drive a truck without an engine brake on it, they are worth their weight in gold to me. If my truck wasn't used for more play than anything else anymore it would still have a banks brake on it. And now that I bought an 02 zf truck I'm kicking myself for getting rid of it and I will have another one very shortly for it too.