I was having the same problem a few days ago as the brown lump seems to defy the laws of saddle fitting - we're on saddle number 3 and saddler number 2 and still only have a reasonable fit so was suggested one of these to help out whilst he changes shape.
This seems to be the official site but if you order direct they've got a 3-4 week lead time as apparently they hold no stock since they make it in your preferred colours http://www.mattesequestrian.com/index.asp
Everything Mattes makes is to order and non-returnable for us stockists so not that many places hold a lot of stock. I hold some half pads and numnahs in brown with sheepskin lining in pony and cob sizes in stock, do pm me if that sounds like it might fit the bill