First off, Jimmyt, where do you live?Some areas can get Mini-Discs easier than others.
There are a lot of mini-disc threads here. You might want to look at some of those first. It'll give you a great overview.
Personally, I don't think they're on the way out. I've had MD for several years, and on my third machine now. Must be about 7 years. My first one finally went and I bought another of my #2 machine, so I am up to owning 3 of them. So far they have all been Sony recorders, as I can find them easiest.
With the newest HD machines you can record for a long time on one disc and they are compact. Anyway, put minidisc or mini-disc into the Lyric and Knowledge Search up at the top. Soon someone will link this thread to many of them.