The ones that you can buy in this country tend to be a bit too small (lime sized) and quite badly made.
They're extremely common in Mexico, you can get big ones, small ones, even plastic ones! And they are THE BEST thing for squeezing lemons.
My wife is Mexican and was shocked when she came here that they didn't seem to exist anywhere.
My point is, they're available here but a holiday to mexico would be worthwhile just to eat tacos and get yourself a decent lemon squeezer.