That one time I bought a pair for a joke at a party a few years ago, I just searched on Amazon for high heels in my regular male size. Apparently, some chinese companies custom-make large-sized lady boots on demand this way. I think I ordered them from "Only Maker", their models seemed to be safe to walk in with wide heels.. I checked before whether you need to order a different size - turns out there is no significant difference. Simply order whatever standard size you usually buy. Just make sure that you pick a model with a wider front. Male feet tend to be wider there, which cause the majority of problems when walking. This is especially true if you have issues with normal shoes being a bit narrow in general (like rubbing at your outer toes when walking for a while).

Also remember that high heels tend to be in the category of "sitting shoes", not "walking shoes". I learned that at said party fairly quickly.