They're not irreplaceable. If you're in the US, I'd let all this go for $10 less than what I've got it listed over here because I don't have the arms to match. T.A. Pro 3-arm chainrings and bolts 42/52

Mind you, I made no attempt to cleanup my hardware, but I think it's looking a helluva lot better than what I'm seeing in your pics

Personally, for little steel bits I keep a small 3" tall Ball jar around with Evaporust in it to soak stuff. I have a tea strainer screen inside to make removal easy.

I never, ever, ever recommend steel wool, if you have this in your shop to use on metal, replace it with bronze wool. Multiple reasons. Steel wool is made out of - guess what? - steel. Steel rusts, and as you use the product it creates steel dust, which will - guess what? - yep, rust on anything you don't realize it dusted onto. Steel wool is also more abrasive than bronze wool, but it's not necessarily more effective, bronze wool may take 25-50% more time rubbing, but it's going to cause significantly less abrasion, swirl marks etc. Bronze wool is no less available, and it doesn't leave steel dust or fragments laying around. When used with a lubricating agent, you can use bronze wool lightly on rusted paint, removing the rust but not the paint. The ultra-fine scratches can easily be buffed out with a fine buffing compound or simple automotive polishing agent.

For something that small, oxalic acid bath isn't worth it. For exterior surfaces, Naval Jelly is great and gets the job done in 10-minute application intervals.

The brass brushes are great also. I watch out for these 3-brush (nylon, brass, steel) to go on sale for $2-3 at the local auto parts stores and big online retailers. I have a coffee can full of them. They're great for "facing" stuff. Brass one is good on fork crowns and other flat chrome. Nylon one is great for clearing old dry wax out of lugs or used with solvent to clean old grease out of threads and races - I use blue painters tape on the handle of my "dry work" brushes so I don't mix the two purposes up. Steel I rarely ever use, because the wire wheel on my bench grinder has similar bristles and is faster. However, it's good for old bolts and getting rust out of holes in fasteners, cleaning up axle threads.