I have an old Ross frame with an .833"(21.15mm) steerer and a 7/8"(22.2mm) headset. The stem is .821"(20.90mm). So the stem is just slightly too small for the headset. The problem is that the stem will squeak unless the quill is lowered all the way down to the headset (where there's a lip). So I was wondering if anyone knows of a stem shim available to solve my problem. Or perhaps another solution to my problem.

you could try using part of a beer can to shim it.

dont use a coke can...thats what a 8 year old would do.

as mention above use a beer car