I use butyl rubber chemical bottle stoppers.
$1.25 each.
I must have a 80 of them around.
Size ten is best.
i got mine at American Science and Surplus locally. Last time i checked, the website did not have any.
I also use tiptoes. Old tiptoes from the 80's
The used to be $4 small, $7 large.
Then I also have purchased dome shaped urethane stuff off Amazon like the $25 ones but way cheaper.
These items work great with my $5K components. And with the cheap ones too.