As far as I know, they are done being made. The first ones I think were a joint effort between OFNA and PICCO Micromotori. The later one was just OFNA. Now that OFNA is gone, the only ones your going to find are ones that hadn't gotten sold yet. Guessing parts will be a bear to find as well if you do get one.
The only mid-block I know of that still exists is the OS21TM. If you have a maxx, I'd look into getting a decent 18, but if you have a revo, you don't have much choice as most 18's are side exhausts which I don't think you can get to work on a revo due to the engine tilt and shock location. There aren't many 18's around anymore either... I think you can still get the dynamite .19T. Kind of a lateral move from the 3.3 though.