Not sure if this means you phoned in or checked the website, but if the latter, then I would try and call and order one over the phone.
The issue with gauges was raised at Shooting Council this morning. Apparently their supplier had a heart attack (but is now recovering well). They did start shopping around for someone else to do them, but the problem of course is volumes - most engineering firms want to do a large run of them. Their supplier has always been good in being willing to turn them out in lower volumes (I think they have identified a couple of people who may be willing to supply smaller volumes in future, but their regular chap is back in business now anyway).
In any case, stock is starting to reappear, so if they haven’t got it listed on the website yet, it’s probably on its way - call and tell them you want it and they might be able to expedite that particular gauge.
If you have called them and they’ve just told you “computer says no”, then email Dave Froggett and elevate it.
In any case, I understand things are moving forward now and availability should improve in the near future.