So here I am talking to myself. Lonely in this thread.
But for those of you that have these types of shanks, turns out their threads must be metric. NPT, compression, etc. all don't work.
So I noodled around the HW store and it dawned on me. If a standard water faucet utilizes a beveled washer (and can hold up to 60PSI) lets try that.
It was hard getting the washer over the tailpiece but that was good since you don't want a leak there either. So now instead of the original washer being like a grommet and being inserted into the cavity of the shank, I have a beveled washer pushing against the outside of that shank. Tighten the nut and no leaks. And an endless supply of cheap parts.
Again, just documenting for someone else...