[quote name='andydye' timestamp='1338220257' post='1671009']
markbass do a velcro one that sticks to your cab (if it's carpet covered of course) an dI've seen one that clips onto a table before too...
[/quote]
I saw the markbass one and thought there must be a cheap way of doing it. So I got hold of a couple of Velcro cable ties from a mate, wrapped one vertically around the side handle of my speaker cab and slipped the other one underneath so that it goes horizontally - and then I wrap this around the neck of my bass to hold it upright. It works pretty well.