Another vote for 26" Mountain bike wheels for a touring bike. A very common size, any bike shop that carries tires will carry some variation of that size.

That being said, I'm surprised that no one has mentioned that if one is stuck with a 700c bike, to make sure that it can fit 28 x 1 1/2 wheels. It will look a bit odd, and most likely force the use of disk brakes, but as mentioned, 28" Westwood wheels was the old size used in most parts of the world, and the shops should have a few tires and tubes lying around.

Note that this is only if they already have a 700c touring bike, judging from the link that OP provided, 28" wheels will fit, but only without fenders. If OP wants fenders on his touring bike, go for 26" wheels.