Before anyone gets the wrong idea from what I suggested I only recommend it if you know how to do so. like what Deb and Ashley said get some experience first before trying it. But yes you right though about it being one of the most accurate ways to sex a snake in my experience.
That’s the problem, there is no one in my area that knows about that.
As much as I hate them, have you tried a facebook group for your area? At least there’s one for my state which make it easy to find local people.
Reptile expos will be the best bet it may take a drive. You may have to ask a few or get to know a few first. Buying snakes are always good ice breakers.