Many are commercially available on DVD in a series called, "UFC Classics". Amazon.com has a bunch of them for sale and you can probably find them on Ebay. I rented "UFC 1," from Blockbuster. It was the entire PPV complete with the floundering announcing team of Kathy Long, Jim Brown, and Bill Wallace.
It's amazing how the sport has evolved in 13 years. "Hey Kathy, did you just drop a chicklet on the announcer's table? Whoops! That's really a canine."