Mike - Split-Six style speed loader is what you're looking for, one that straddles the belt. These are my favorite kinds of belt-based speed loader carriers. The biggest problem I've found with them is, I don't like snaps/flaps as retention devices and there are only one or two split-sixes that don't rely on snaps to keep the loader in place. Barranti's Speed Pouch: http://www.barrantileather.com/New_Products.html (about half-way down the page), marks the first time I have seen a leather one. I haven't handled one in person, so I cannot give an opinion on how well it works.
Here is a setup (for all of you carrying speedloaders) that works like a charm: http://www.safariland.com/DutyGear/p....aspx?pid=CD-6 - The CD-6 alone is not sufficient to keep a speed loader in place, they wiggle loose frequently, the steel just doesn't have the tension to keep a slick sided speed loader in place, even if you bend it in (you need to with the 5-round J-Frame loaders), whether it be an HKS or Safariland COMP, whatever. You need to add some tension and after some late night brainstorming I realized the easiest solution. A CD6 + http://www.staples.com/Staples-Econo...product_831636 - Put the CD6 on the belt, insert speedloader, wrap a rubberband, a hair tie, or even a properly sized rubber O-ring over it and ET VIOLA! Properly tensioned, open-top, speed loader pouch, that straddles the belt. Works like a champ, I run two of these inline, in front of my holster (if at 4 o'clock) or behind the holster (if AIWB).
I have jogged, worked out, worked full normal days, driven, etc with this setup for about 3 or 4 years now and it works. In fact, I even rigged one upside down on the off side strap of my upside down shoulder rig and drove 500 miles with it and it didn't so much as shift. I will admit, if you run a rubber band/hair tie it gets kind of irritating to practice drawing them from the belt, you have to reloop the band every time you draw. The best solution is a rubber o-ring, so you can pull it off and roll it back over the top once you insert the loader. I just took the biggest and smallest speedloaders I have and CD-6 down to the autoparts store and tried a bunch until I found ones that fit. I forget what sizes they are now, I want to say 1.25" inside diameter for J-Frame, and 1.35 or 1.45" inside diameter for L-Frame loaders, but don't quote me, best bet is to try out an assortment yourself.
I ran a few different holsters AIWB for a revolver, but can't find anything that works better than the SN-2 from Bobby Mac's: http://bobmacs.com/products/holsters/iwb - Southnarc & Co designed a great AIWB holster for a revolver on that one. Pricey yes, but you know that old aphorism - Buy once, cry once.
-Rob