I am going to try and find the curved bulkheads. I don't trust the uniseal because if I accidentally bump into it, the seal may losen and leak. Failing to find the bulkheads I will try to find some thick rubber bushing or just end up making something like Tony mentioned.

I've used the common type bulkhead that you get from Hydroponic stores on various sized containers, without problem.

Measured a small one I've got, it's for 1/2" tubing (barbed) with a bulkhead face of 1.25". Looking at it against my ASM G3, could see using it on the skimmer without overly distorting the chamber. A hydroponic store might even have smaller but still sufficient for a skimmer recir mod.

Let us know if you do find the curved bulkheads.