I couldn't find actual glass holders for my move. What we used were really for appliances. The rental place wasn't too keen to hear what I had intended to use them for and made it rather clear that it was my risk if I wanted to use them for glass.
The glass ones use at least three suction cups per handle. Supposedly very expensive to buy (something like $750-1000)? Too bad, something like that could come in handy once in a while ...
Anyhow, any tool rental place ought to have the appliance cups. I wouldn't rely on them for anything other than lifting the tank off the stand (and perhaps final positioning onto another stand). Once you have a gap underneath it, then get a hand underneath. Definitely don't carry the tank by them solely.