Shimming Interspace arm to adjust azimuth

The headshell on the used Interspace arm (on Horizon tt) I purchased recently is rotated slightly clockwise so that the stylus points inward toward the spindle. I've made sure both platter and armpod are level and verified that the cartridge itself isn't the issue. Since the Interspace arm doesn't appear to have an azimuth adjustment, I'm pretty sure that my only option is to place a shim between one side of the cartridge body and the headshell.

Can anyone recommend something to use for shims? Should I use a thin aluminum washer? Does Home Depot or some other on-line electronics store sell something that would fit nicely around a cartridge screw? My carts are a Shure m97xe and Dynavector 10x5.

Thanks for your help!