The more serious free divers generally use a rubber weight belt as it will stretch a little and allow the belt to be positioned lower on the hips away from the waist. The stretch will allow for wetsuit compression during a dive and the weights won't move. (The rubber belt will also "stick" a little more to the wetsuit too).
Having the belt lower on the hips allows more freedom to breath.
Some friends of mine dive with a weight harness as this moves the weight away from their waist and they like this as they have bad backs. It also changes their trim as the weight is positioned around the chest rather than weight.
This link will take you to a page showing 3 weight systems and various weight related products. It is specifically focussed on free diving. (Although it is in New Zealand and nowhere near you).
Weights & Weight Systems - Freediving - Ocean Hunter
One key thing for free diving is being as streamlined as possible. This is more important for free diving than it is for SCUBA.
What ever weight system you choose for free diving make sure:
1. you can drop it easily in the event of an emergency
2. you can adjust the weight so you can move from suit to suit and also remove weight if you are starting to dive deeper
3. It is as streamlined as possible. Drag is the enemy of a comfortable free dive.