Welcome to the forum
Wincrasher posted this bike holder link: http://www.thule.com/en-us/ca/products/ ... 01-_-18344
You might be able to adapt something like that. Maybe mount it to a piece of plywood or use a cargo strap to keep the bike from moving around.
Look at fork mount carrier fittings also. That wouldn't cost much. Again, maybe mounted to plywood or van floor.