Gel belts/pouches

I've got a stretchy running belt which is fine for keeping a few gel packs, more than that and it's hanging down on my bum and threatening to fall off.

I'm not a quick runner, and in a very heavy sweater, so I was planning on taking 7-8 gels on my marathon next month.

Has anyone got a suggestion for a fairly secure solution that can carry quite a few gels?