Replacing or reinserting [headless rivets] (?) on stands

I do not know what they are really called, but I'm talking about the small hollow cylinders that hold parts of stands together. I have more than a few that are falling out of my cymbal stands and bass drum legs, and I'd like to know how to reinsert them permanently or where to get new ones and how to install them. Would definitely be better to spend even a few dollars on some new small parts than about $200 on new hardware.

I think what you are referring to is a roll pin, or a slotted spring pin.

http://en.wikipedia.org/wiki/Spring_pin

You have a couple of options.

You can remove the pin by lightly tapping it out with a punch and a hammer and then replace the pin by lightly tapping it into place.You can get replacement pins at a hardware store or automotive parts store.

I had an old Gretsch Blackhawk stand that had a broken roll pin. I ended up drilling out the pin and using JB Weld instead of replacing the pin. that was about four years ago and it's still holding strong. I use the stand for my home kit, not the gigging kit.

A simple small bolt and lock nut work fine. I've done it many times. 10/24 usually works. Might have to use a thin washer.

If you are talking about rivets, you can buy a rivet installation tool. There are different types of rivets. You want the large tool that can install strong steel pop rivets.
Use a drill to remove the old rivets. If the hole is worn then drill the hole larger for the next size rivet.
The heavy duty installation tool is expensive. About $180 US. You may be able to rent one at a tool rental shop.
http://www.zoro.com/g/00014244/k-G2212576?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kpid=G2212576&gclid=CKOF5qvAhb4CFc9AMgod1lwATw

Sometimes you can tighten the existing rivets by squeezing them tightly with a large vice grip pliers or laying them on the anvil section of a vice and hitting them with a hammer.