Get a battery operated bubbler. They are $5 - $10 at Walmart. Check in the sporting goods section in fishing where they keep the minnow buckets. Put it on the side of the tank and drop the air stone in.
I so agree with Crisper, fish are way tougher than you think. No need to bother with oxygen for a 40 min ride. I just wouldn't put a 9" knife in a small tank for transport. Get a rubbermaid bucket or a cooler instead.
Battery operated bubblers are only a few dollars. I just picked up new tank and the fish that came with it. I used a bucket (from my LFS) with a lid and just to be safe I put in a battery operated aerator. The drive was about 45 mins. Worked like a charm.