True spring steel is available from Brownells.I think its 1095,but I could be wrong.
I don't doubt your success with O-1 extractors,Gunplummer,and I have seen Mauser claws,aftermarket,that were supposedly O-1.In my experience,while O-1 is a good,usefull tool steel,it can be a bit brittle.
I will confess I often have chosen O-1 for the convenience of the drill rod or flat ground stock,and also my torch,eyeball,and oilcan heat treat system may have lacked process control.
From a knifemaking book I have I learned many circular saw blades are L-6 carbon tool steel.That may be good to know.
Flat ground and drill rod in tool steels like W-1,O-1,A-2,D-2,S-7,etc can be had from MSC.But,no joke,you can probably find it on Amazon!Aircraft tubing,4140 seamless drawn over mandrel,look to MSC or maybe Aircraft Spruce.They sell a lot of good stuff.Composites,graphite,kevlar,epoxies,polyesters,balsa,spruce,etc.
8620 can be had from McMaster Carr.Plenty of good receivers have been made from that.It also case hardens well.A great steel to have around for general gun parts.
If you can find a shop that builds or repairs plastic injection molds,there is a pre-hard mold steel called P-20.If I recall right it might be Rockwell 24 to 28 "C"?.Something like that.Pretty useful,polishes well.
Look up "mold core pins" and "Mold Ejector Pins" in the MSC or DME catalogues.Learn about the steel,and grades of hardness.They are H-13 hotwork steel.You can get some high grade tool steel,already heat treated to about as hard as you can machine with Hi-Speed for one grade "C" pins,I think,"CX" pins are harder,up in the 40's R "C".You can use carbide or grind them.Ejector pins are surface nitride to high 50's R"C",with tough cores.Available as pins and blades.
17-4 ph is cool.Machines great,semi-stainless.Precipitant hardening.That means a couple hours at 900 Deg f gets it up into the 40's Rockwell "C",with very high tensile.No warp.
An allen wrench can be a useful piece of stock.
ETD 150 and ETD 180 are "elevated temperature drawn" carbon alloy steels.Thats sort of like work hardened.The tensile on them is 150,000 and 180,000 psi,respectively.
"Stressproof" shafting is a workhardened steel bar.Not real hard or special,but better than 1018 cold rolled mechanically.
I don't recall so well right now,but seems like 1057 or 1157? was a good carbon steel for small case hardened/carburized parts and tools.