Yup, KTM is impossible to get parts for once it leaves the showroom floor.
I must say though, my KTM 495 is pretty much the best trail bike I have ever ridden, over taking Maico but Maico is still up there as a great trail bike, the KTM is like a Maico with a little bit of steroids. Now, the 495 I have is the 1984 model with the 5 speed engine, both make the difference, the lower compression and bottom end power of the 1984 modeled with the 5 speed gear box with a 1st gear so low makes single track even easier than on a Maico. Just don't break anything because you'll never ride it again.
There are places that manufacture Maico parts and a lot of Maico bearings are standard as well. Plus, Maico being a small factory left few changes each year meaning that certain parts are the same for many years and not only that, but even the 250 and 490 for example share many of the same parts including the frame. Actually, before 1983 they actually shared the same cases, the 250 had inserts into the crank case to make the crank volume smaller.
There are certain parts though with a Maico that pretty much are like giving away a bike. the clutch basket is one that is harder to find. Any 1982 special frame parts also, that's the bastard year, they don't like to make for example the special brake rods for that bike or bling brake pedals.
also, kostler in germany is making some of the parts from 78+ new as well. Thats where I got my clutch basket for the 82.