It doesn't take much to make a buffer. I've seen them made from old dryer motors. You can even make them from a wood lathe if you have one. The other option is to just keep sanding it with finer and finer grit by hand. I've done this down to 1000 grit and it works just as well as a buffer. It just takes more elbow grease.
When I was about 16 years old, I was given three old farm motors. I bought some arbor adapters for about $5 each and have been using them for over 20 years now. They work great. Just be sure to put thread locker on the set screws. You can even put a buffing wheel into a hand drill motor and then clamp the drill in a vise.
I thought that I should say a bit about buffer safety. They look harmless and a lot of people don't realize how dangerous they are. The unique danger with cotton buffing wheels is how "grabby" they are. They will literally grab your knife out of your hands and throw it right through you. One friend of mine had his knife get shot through the wall of his shop and into the next room.*
Hold the knife in a "break-away" grip. Don't get your fingers wrapped around it or worse yet, through any holes in the steel. It could break your fingers if the wheel catches on the knife and tries to pull it out of your hands.*
Be sure the wheel is spinning toward you from the top. Then use the bottom half or third of the radius. That way if it does get thrown, it will get thrown down and away from you. If you try to use the top of the wheel, it will get thrown right at you.*
Buff the bottom half of the knife, then turn it over and buff the top half. What I mean by this is that you don't want to give the cotton a 90 degree angle that it can grab onto.