A skateboard helmet is a good option. We did it with some hole drilling, bolts and a couple cheese plates. We also had a Paralinx wireless video transmitter on there and a mophie type of replaceable battery on there to power the battery pack. The most important thing was to have a back weight on the opposite end of the helmet of the camera. No matter how well you secure the chin strap the camera will still want to fall if you don't have some counter balance.
It's also important to get some beanies that you can wear so that you can really get a snug fit. I would always have at least 2 on so that the helmet fit nice and tight. We used the rig for a series of commercials. We used them for 3 days straight.