FWIW I located a decent source for some cheapish 6061 alloy discs:
https://vi.aliexpress.com/item/1005006973943538.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.1.2c54nLujnLujeg&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40196.404796.0&scm_id=1007.40196.404796.0&scm-url=1007.40196.404796.0&pvid=75ca5da4-8175-49ad-8173-f9e908a10711&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40196.404796.0,pvid:75ca5da4-8175-49ad-8173-f9e908a10711,tpp_buckets:668%232846%238116%232002&pdp_npi=4%40dis%21USD%2110.75%2110.75%21%21%2178.10%2178.10%21%402101c5ac17354659910146186e841d%2112000038907149219%21rec%21AU%21704119413%21X&utparam-url=scene%3ApcDetailTopMoreOtherSeller%7Cquery_from%3A

100mm x 30mm thick is ~$USD30 delivered from China. WOuld be a lot easier on Norm's lathe than steel - point taken on longevity etc - but I think for domestic usage - the 6061 would be as good. Just an idea anyway - you guys are amazing with your ingenuity. Very impressed.