Cracked Grey Tank

[Madmax07]

Unfortunately, one of our grey tanks on our 3582RL sprung a leak this summer. We've had it at our RV dealership since the end of August. The plan was to replace the tank. The dealership told us that the crack is about 8" long and runs along the seam of the tank.
My understanding is that the seam runs horizontally around the tank. We did use the trailer once by simply leaving the valve open on the grey tank. This is the tank that holds the wasted for one of the bathroom sinks and the shower.
Our problem is that the dealer has told us they are having problems getting a tank. They claim there is only one supplier in the U.S. (we are from Canada) and that the supplier has no inventory. I'm a little skeptical but there is no reason for them to not be truthful.

I asked about the possibility of repairing the tank. They said they could try to repair it but that it doesn't always work and would not guarantee it. Has anyone else had experience with getting a grey tank repaired? Am I better waiting for a new tank or would it be worthwhile to give the repair a try?

Also, anyone know of suppliers for these tanks?
Any help would be appreciated.