I picked up a Tektronix 2221A the other day for a very good price, its main flaw is a couple broken knobs.
I need a Volts/div knob, I tried epoxying mine back together, but it didn't hold. If I can't get one, I'll bore it out and glue in a metal sleeve, but a new knob would be preferred. It is just under 3 inches long, hopefully it was fairly common in other models too.
I need a VAR knob for the Sec/div, it was totally missing on mine. Not sure what it looks like, but it goes on a 1/8" shaft with a set screw and it can be pulled, so I don't think it was like the ones on the Volts/div knobs, those would be too hard to get a grip on.
I need a flexible coupling for the shaft of the Volts/div VAR knob, I assume these are common, it goes on a 1/8" shaft. I tried looking on McMaster-Carr, they have things that will work, but they are meant for heavier duty applications than just a knob and are quite expensive, I don't need it to be able to handle 6000RPM and 20lb*ft of torque. I think I could probably replace it with a piece of rubber hose and glue, if I absolutely had to.
I need a couple of the shafts for the VAR knobs, one on the Volts/div and one on Sec/div, but they aren't super important because they are just 1/8" nylon, I can get 2 feet of it and replace them all.