Are you talking about something you roll the front wheel into? Like from Baxley or Condor?
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I've got a Baxley chock and it great, but not cheap. Also, it's not the same as a stand. Sure it'll hold the bike upright and pretty solidly like a stand, but unlike a stand the wheel isn't off the ground. So if you're trying to do some service item, even simple ones like chain cleaning, a stand is what you need. Chocks are great for parking, or extra stability if you're doing some heavy duty work (that doesn't involve the front wheel/suspension) - but they aren't interchangeable.
If you're going to get one thing only - get a rear stand. You'll get the most use from it.
Webbikeworld (great site) has a section on lifts, stands and chocks.
http://www.webbikeworld.com/motorcycle-lifts-stands-wheel-chocks/