The 30 amp is a special configuration but a 50 amp is available in the USA at any Home Center. It is commonly used on electric stoves. Brian: Aren't you worried about theft??
If you mean the plugs and outlets - Yes - available in the US - but maybe not in Mexico - can be hard to find if not impossible in Mexico. I have not seen the RV configurations available in Mexico. Whatever plugs are commonly used for RVs and outlets in RV parks and campgrounds can be found or modified for use - but not easy to find in Mexico - I think I bought the ISB and took it back to the states with us and did my wiring there. It may be possible to find the correct parts in Mexico but I don't know where. I don't can't remember where I got the 30amp plug but I am pretty sure I got the 50amp stuff at Home Depot. Again - may take creativity.
I have a cable with a lock and use it depending on where I am. Many places in Mexico - at least many where we go - are pretty safe - and not a lot of people would know what this thing is or what to do with it - with my plugs and outlets on it there could be even more confusion unless another RVer was the thief. But I have a long bicycle type cable I made up myself that I can wrap around a tree or part of the RV to make it very difficult. But if someone really wants anything they can find a way to get it. Houses are broken into and semi-trucks stolen all over North America and the rest of the world. We do take precautions but we also try not to worry. Life is too short to spend too much time worrying.