You're looking for "grits" from lapidary suppliers, as raymo mentioned.
If you go further down in the forum, in the
ATM and DYI Projects section, you will find several threads on this topic and that's where the mirror grinders hang out. The first "sticky" at the top of the section is all about mirror making.
Getting the grits is the easy part, however, I found finding the glass much harder to do, but if you really want to try it, it can be done.
My only caveat is do it because you want the experience, not because you want a scope. If you want a scope, go buy it! But if you're simply curious about how its done then by all means go for it. I'm just making this comment as I've found some people don't realise how cheap telescopes are these days and are still under the misconception that its cheaper to make one - no, its not! In fact you'll probably find it cost more to make it yourself than it would to buy it off the shelf.