If you can find them new you will be paying all kinds of money for them. and they will still probably need minor machine work done. Your best bet would be to get your repaired if they are
****, broken etc.
If they are not repairable or you don't have any case halves is to get them used in decent condition, (ebay is a decent place if you cant find any on here) then have them reworked by a shop such as HPR.
New parts are hard enough to find for the 87+ bikes much less new, OEM 85-86 parts. Just like Jerry said, there were not many of the 85-86 bikes produced compared to the 87+ models.and there were probably even less OEM cases made which have probably been bought, used and blown up by now.
I had to learn that with an LT comes the territory of getting good used parts and having them worked over. New parts OEM and aftermarket is not something these bikes have a lot of, unlike the Honda 250r which has a HUGE aftermarket.
Sorry to be the bearer of bad news.