I usually find the other finer grades of ScotchBrite at stores selling auto finishing supplies. Auto Parts Stores usually have a finishing section.
There happens to be a good wood shop near me that sells it as well,,but at premium prices.
There's always the 'net' I guess.
I don't recall the actual grit #'s, but I buy the gray and the maroon colored pads.
The white colored ones are even finer but to tell you the truth, I haven't had much luck with that grade at all. No cutting action,,not even the feel for me when using it of using 0000steel wool.
I've pretty much omitted the use of steel wool in my shop. Once in a great while on a wood finish that has the pores filled and is very hard I'll use it to knock down the gloss. Other than that, it just seems to always dump on you with a few shards of shiny wool stuck in an otherwise perfect finish. Always discovered of course when everything is all done.
Scotchbrite for metal polishing too. Use with oil for a nice burnished finish. Same idea as using a wire wheel w/oil.
I use a gray or maroon pad (dry) for the last polish before a rust blue job on many occasions. If I get a streak or small spot of discoloration in the finish as I go along, I use a small piece of the same grit pad to gently polish out the problem. You will remove some of the color of course, but the polish lines are preserved. The next coating/cycle or two will bring you right back up and even with the rest of the work.