"Sleeving" A- body brake drums?

Aftermarket will run a lot of X thousand pieces for distribution when the market demand is great enough. Droughts are common in parts for other brands too. I remember when a friend needed 2 axle bearings for his 63 Impala. Davis Auto Parts had the only 1 left ( showing on vendors inventory anyway ) in the USA. They did find another and ordered it in from Canada.