Irvines bring up Martin reps on occasion. I would contact them Terry, and see if they have plans on bringing one up sometime soon. The other alternative is find someone else who is successful in getting their Martin to fit, help you out.
On a side note, there is more to saddle fit than gullet width! I'm not taking anything away from the Martins, had two and loved them a d they worked on a couple of horses of mine but I started running into problems on another horse and could never use them on my hubby's VERY short backed gelding as I could never get the saddle behind his withers like they are supposed to fit, cause there was no back left, and to sit on his wither/shoulders would have required a gullet width I don't think even they make. When I set the Martin behind the withers/shoulder blade of my other gelding who has a very long sloping shoulder I ended up with my saddle positioning me over my geldings lower back area, loin area. Needless to say this made that area very sore, to the point he bucked me off, as I was slow to catch on cause the gullet fit was fine. One needs to take into account more than just their horses back width. You need to look at the slope of their shoulders and set of the withers, the length of the back etc. I ended up with a saddle of standard gullet width to fit this gelding who does have massive shoulders, but it is very flared in the shoulder area, and short in the skirt so I'm not sitting on his loin, and broad in the back and seat to fit the width of the back. I need only change the pad I use nd can fit all 5 riding horses. THIS is how I like a saddle to fit and I'm sure one day I will find the horse it doesn't fit, but I've done the whole fit the saddle to a specific horse route and believe me it's nice to find one that fits the majority, sure easier on the pocket book.