I bought a floating water pump that draws in air for about $20 at Acadamy (I've seen them elsewhere as well) that I rigged to plug into my ciggarette lighter. I run the 16 guage wire out the back sliding window and I can keep a lot of fish alive for a long time. I don't knopw about trout.
The best thiing is that it can be put into any size cooler or barrel or even 5 gallon bucket.