Smaller heater box options without a/c

[NJM73]

I am looking for options for a smaller heater box that I can move totally into the cab. Kinda of like the aftermarket ac boxes but without the ac. So far mojave heaters are the only thing I have seen that look like they might work. Are there any factory boxes from other models that would fit well? Wont have a source for vacuum so the box needs to be able to function off of the factory switches or electronic switches
Thanks