A quick Google search didn’t show any masks for sale that were specifically El Sapo Dorado, but since (to my knowledge) El Sapo Dorado is a fictional Lucha Libre wrestler strictly from The Middleman universe, that’s probably why.
Looking at sites that sell Lucha Libre masks in general, there’s the El Guapo mask here, which, despite being navy and yellow instead of black and yellow, seems to be at least fairly similar. It doesn’t have the yellow on the forehead like El Sapo Dorado’s, though.
I’ll keep an eye out to see if I can find anything better. Followers, do you have any suggestions on where to look? You can put them in the askbox and I’ll post them for thatlever to see.