There are light duty wheelclamps around which may suit your need but are easier to remove by thieves!
I personally don't see the point in light duty security. I've just bought a Bulldog Titan wheelclamp (Sold Secure Gold Std) but I wouldn't recommend it to anyone with mobility difficulties as it's quite heavy and cumbersome.
Hitchlock, alarm, or leg locks would all be easier to manage - if your insurance requires a wheelclamp, fit a light duty one but add one or more of these as well.