Just don't buy a Yellow Jacket. Had one at the old shop I worked at. It sounded like a bad techno song and it couldn't find gas if you farted right into it lol. Too many false positives too.
I had this old one I picked up off a retiring tech. It had a leather pouch. I gave it to my best friends dad as he is a soon retiring HVAC tech. It was awesome at finding leaks. It was a shame that it wouldn't handle anything newer than 134a or I would still have it.