The MX switch G80-1800's come up on ebay (US) every once in a while, but usually are overpriced when they do. There was some 1865's on there for a while, but those are gone at the moment.
There are always plenty of junk MY switch G81-1800's on ebay, but unless those have double shots or a case for harvesting, they are worthless.
There are a couple US based online stores that have them at ok prices, and of course tons of them on Taobao.
Is there a specific model you are looking for? if there is someone, like maybe Lysol or myself could probably point you in the right direction.