Thanks for the offer Pete but I'd rather you didn't take a chance on bringing them through US customs as the legalities of where they fit in the ITAR rules isn't clear.
If you'd bought a fifty cal you'd just sail through but a couple of speed loaders might get you the full cavity search!
I will persevere, I found some on the Helston Gunsmith web site but they are six round ones. I've e mailed them about a seven round one but await a reply.
Incidentally, if you have a slot for a 105mm Pack Howitzer on your FAC, Helston have them in stock together with some armoured vehicles to tow it with.
They've also got some spares for that 30mm ADEN cannon that's sat in your garage awaiting a firing pin.
http://www.helstongunsmiths.com/