Firstline Training Center Hockey Training Center in Rockville MD is auctioning off their equipment. AFAICT, the sharpening machines and synthetic ice have already been sold. :(
It is very close to the Rockville ice arena.
https://rasmus.com/auctions/134ElNk9ZbjdAz8uLA4R/a/BANK-ORDERED-LIQUIDATION--Indoor-Hockey-Training-Skating-Center--Rockville--MD
EDIT: it looks like the auctions closed in 2023. So I think it's too late.
We all know that a lot of ice rinks go out of business every year. Maybe it is possible to look for auctions and notices of business closings on the Internet to find ice rink equipment?