First off I'm not an expert but I did alright with a batch of about 30 rainbow trout this size or larger (6 - 8 inches) for a bit over two hours. I think a cylindrical cooler would work better than a rectangular one like I used - no corners for the fish or water to slosh into. I believe it's harder for the fish to hurt themselves by running into a wall with a cylindrical transport tank. Having more space inside isn't necessarily a good thing either, if it just means hitting a wall inside the container. You do have to be able to get them enough oxygen though.
I used a regular (for the USA) 120 V air pump and an inverter hooked to my cars cigarette lighter. I should mention that I had access to an oxygen tank and regulator as well. If the waters cold enough it should be OK without.
For smaller fish than what you're transporting or maybe even up to the size you're getting, I'd probably use 5 gallon buckets with tight fitting lids and airstones inside a cooler or coolers (with an air vent near the center of the bucket lid). At least that way if it spilled it would be contained.
I don't know if you have access to any coolers like these but with modifications some of these would probably work well for larger fish - http://www.homedepot.com/p/Rubbermaid-10-gal-Orange-Water-Cooler-FG1610HDORAN/202260809
On some coolers like this the lids screw down which would help limit spillage. Keeping them stable might be a bit more of an issue because of the shape.
I'd use multiple containers but I suspect some would think these containers are too small, I don't know, they could be right but that's my 2 cents worth
FYI: I found a review on fish transport that might have something you can use - http://www.fao.org/docrep/009/af000e/AF000E05.htm
edit: Forgot to mention that you might find a good transport tank available as a bait tank - for example - http://www.catchnbait.com/keepalive-shad-bait-tanks.htm
Cheers