Motorola stopped semiconductor production a while ago.
All process and device production were taken over by On Semi.
You can obtain samples of the IRF830 from On semi up to 5 pcs I think FREE!! if you register and order samples on line.
Might be best if you register as some sort of engineering development I recall very many years ago medical physics departments did develop electronics from scratch design as I did in leeds 25 years ago!
http://www.onsemi.com/site/products/summary/0,4450,IRF830,00.html
You may find that the web ages of Shirlab of use for tracking down the ever changing state of who is buying who in the electronics component word it's also very handy to track down component manufacturers.
http://www.sherlab.com/electronics/os.html Hope it all helps if not have a nice day.
ps anyone reading this want a experienced X-ray engineer or medical electronics technician in the yorkshire area?...also availabe as a consultant service for the samegood luck
paul