There are so many of these MTB's produced for so long, and in so may classes from Walmart grade to artisanal Ritcheys and Fat Chance's, that there are still millions of these floating around, in almost every suburban garage. You will be able to find used parts for these till kingdom come. These MTB's will outlive cockroaches.
But for the time being, your bike is still a perfectly fine bike. Just get some tubeless wheels and tires and put them on and enjoy the bike. That is the one upgrade that is a must-have for these older MTB's.