My advice is don't buy a snake unless you can handle it first. I've worked at petsmart and I found that the hatchlings came with one of three personalities-
Curious, nervous and "I'll rip your face off human!". Since you already had a bad experience- you probably don't want a snake that needs time and patience to mellow out. When you buy the snake I would also ask the staff- since they likely know the snakes normal temperament.
I would recommend Petsmart- but not every petsmart is as good as the one I worked at. But I would definitely recommend finding a store that will let you hold the snake first.
Good luck and way to go on overcoming a bad experience!