You can get RCA shorting plugs here.
And you can get XLR shorting plugs here.No need to pay sky high prices for Cardas
Actually the Cardas plugs are non-shorting:
" ... Unlike traditional shorting plugs, these caps do not short the inputs. Another difference: They completely cover the RCA input with a solid shield comprised of nickel and brass ..."
The same seems to be true of the AQ plugs:
"... The AQ Noise-Stopper caps are grounding plugs (not shorting plugs) that help you block out this unwanted noise ..."
I've never tried any of these.