[Kidkraz]

I've replaced my old one and I've not had any issues with mine before or after replacement. I've had it go off once, while using a can of what I thought was compressed air. It was one for cleaning computer equipment, well it went off and once I read the label on the can, I realized it wasn't air, but chemicals. I aired out the camper and no issues since.
Amazon has them, but not the version you have in your TM. Seems the 70-742 version is out of stock at most places. I'd see if the factory is still using the 70-742 or another model.