Resolved. I've just bought a Oasser P1 mini inflator to keep in the topbox when travelling. It's nice and small so takes up hardly any room, powerful enough to inflate both tyres and is cordless, it can be charged either by mains or run straight from the topbox or glove box power sockets. It is easily preset to your required pressure and has a couple of LED lights. Seems a good bit of kit. More importantly it's a push fit so no worries about thread length.
I've never heard of that one before, sounds like it's got some unique features, built in battery but if it's flat you can bypass it by plugging into 12V?