I know this is an old thread but maybe this info will still help.
First, the Montanas were made by LS tractor of South Korea and they were put together in the US. They were powered by a Mitsubishi diesel engine. And he can still buy one. But it won't be green with a Montana badge. It will be blue with an LS badge. LS now sells them and has dealers all over the country. Here is their website. LS Tractor USA
If you do a dealer search it will only show the closest dealer to your zip code so you may need to call to find other close dealers.
FYI, I just bought (more like stole) one myself. A '06 model 4540 (45 hp) with loader, a brush grapple, rotary mower and box blade.
You didn't mention the model you were looking at for $10K but that sounds like a good price for almost any Montana model with a loader, low hours and 4 pieces of equipment.