if you get a large ziplock bag and put just enough water for it to be comfortable and are able to keep it in a box or something so it doesn't slide around it should be fine. Depending on fish size I like to keep a betta cup around for fish transport (the larger betta cup like petco has) hope that helps
A decent tip would be is to keep the plastic bag you got the fish in from LFS.
Then can be used for transporting fish back to LFS or for re-homing.
I always have a couple of these bags in cupboard just in case.
Edit - I also put the plastic bag with a few inches of water with fish and try to get as much air inside bag and seal with either ziplock or elastic band. Then put bag inside a bucket and roll a towel inside bucket next to bag so bag does not roll about too much then cover bucket with another towel. Darkness for fish will help stress levels a little bit.
At last someone with common sense (Ch4rlie) instead of a bucket I use a polystyrene box as said darkness is best for stress relief. Just a tip don't feed the fish for several hours before bagging them up this will help with pollution of the water.