I do believe that they are not existing here... I have asked a couple of big webshops about plants and they didn't had any idea about it.
I have found some deep water saucers and I was thinking to cut these and make my own humidity trays, since the extra long water saucers are too shallow to place those [hydrokorrels] as they call them in Dutch here.
I live in Den Haag and although outside the humidity is 80% to 90% inside and at where are the orchids (windowsill and below is the radiator) the humidity hardly goes to 50%. And I would like to have at least 65% so my orchids could be the happiest
It reaches 50% after I have put three large bowls filled with water on top of the radiator. And the radiator runs at the lowest temperature (barely warm when you touch it).