I have a TTWeights clamp that was designed especially for the Rega tables. Actually, it's a record "weight". It doesn't clamp per se, but sits on the spindle. I think it works and sounds great.
http://www.ttweights.com/catalog/item/6997332/7020292.htm
http://www.ttweights.com/catalog/item/6997332/7020292.htm