I say find somebody local to you that knows how to sex a snake then ask to see the snake and then have them pop it while you distract the person that took the snake out. Then if it turns out to be a female buy her.

Now I can almost guarantee you right now that it's a male because they in turn got it from a breeder for probably slightly less than what a male normally runs for and in turn they jacked the price up to make profit. The person who sold them the snake knows it's a male. They don't know because they didn't ask them.