Do you mean a record clamp? Those clamp onto the spindle and hold the record flat.
If I recall, Michell makes a clamp specifically to fit Rega players. Before I did the Orbe upgrade (it comes with a screw-on clamp), I used a Sota clamp that worked very well.
The only weight I know of is the perimeter clamp that VPI makes. That is a metal ring that goes around the outside of the record. They are very nice, but the price might be a little more than you're expecting.
If you have records that are warped, there are a few solutions. You can buy devices that flatten records, however, they are not inexpensive. Some people put records between two heavy pieces of glass and leave that out in the sun for a day. I haven't tried this (yet) but have read of excellent results.
Even then, I'm still a big fan of record clamps. They tightly couple the record to the platter and benefit even flat records.