Condor wheel stop. I highly recomend it. I had one in my pick up bed when I had a spin and accident on my way to Daytona last year, bike never moved. They have a nice monting system so it can be removed and used as a free standing unit to work on your bike.
Baxley sells the LA Trailer Chock. I saw it at Steel Pony Express....very impressive. Also saw their trailers. Incredible engineering but very expensive.