When I stop during a ride to lube ny chain or fix a flat (rear tire) I just slip a 13" tire iron under my skid plate near the foot pegs oppisite the side stand and rock it up on the side stand. (not an uncomon practice for bikes with no center stand)
I don't know about the rest of you, but I have to be very careful to keep the bike from rolling forward or back and sliding off my home made trail stand.
Here is my 10 cent solution.
I just found a thick O-ring of just the right size to loop around the grip and back through itself and then around the end of the brake lever. Look a motorcycle parking brake :P
I tested this while cleening my chain today and using my trail side prop method, and no matter how rough I was with the rear tire the front tire didn't budge. the O-ring holds enough pressure that I cannot roll the bike while it is installed.
I use a steel braided, well bled, brake line. This may not work as well with rubber brake lines.
I found about a 3.5" diamiter and as thick as possible O-ring worked best for me.best of all, it adds almost zero weight, and takes almost no space to cary.