You can use anything that holds water to vacuum water in. I bought a 5 gallon water jug with a handle and spout from wal-mart. It works great to empty and fill without making a huge mess.
Quick tip I learned with vacuuming. Instead of fitting something that big under the bath tub faucet. Run your water about the same temp as the tank and stick your hose under the sink faucet and have it drain out into the bucket.
The huge benefit is that it's hands free. Once you get the hang of it, so I'm changing filters and cleaning algae while it takes about 10 minutes to fill.
The tricky part is getting just the right amount of water coming from the sink faucet so it doesn't over fill the vacuum hose and you just waste water or not enough and the hose doesn't really have suction heading towards the bucket on the floor.