To go to a store that sells them and get a demo.
PCW/Jessops/John Lewis, even larger Boots[I got mine there]
What exactly do you mean by stand alone?
They all work from mains electricity via a transformer as far as I can tell-I have not come across a battery version.
Some wqork from an 9internal memory load bis a USB other have slots for media cards.
Hands on is the only way to check out