I know pretty much the route you are likely following. If you know that the air tank is leaking
and can not find a shop/person for a replacement... a good emergency 'fix' can be done with:
It is a JB Weld epoxy product that comes in 2 sticks. You'd have 5 minutes to
rub the two parts together and apply it, like a ring, around the 'neck' of that tank. It sets to
full cure in an hour, so you won't have to wait too long to get going again. The epoxy putty
'mushed into' the area leaking will likely get sealed. Just be sure to drain the air pressure
before you apply the putty.
I've been in many-a-jam along dark, empty roads and this type of product can be a life-saver.
Hope you are ok and no longer in need of help though.