From Biketek this Self Assembly Motorcycle Wheel Chock will support the front wheel of the bike during storage and transit. It is fully adjustable to fit wheels from 12" to 18" and with the optional adaptor kit will cover up to 21" diameter wheels.
It feature a pivot clamp which locks the front wheel securely by the bike's weight. It can also be bolted down.
The optional adaptor kit has a replacement support strut to cater for 21" wheels (narrow MX wheels only).