1976 KZ400S Leaky Petcock Problems

Does anybody on here have a '76 KZ400S, and if so, what are you using for a petcock? The one that came on my bike is OEM, but it leaks like a sieve. The new one I got off of Amazon (1) looks like an OEM but doesn't fit - the holes are a few millimeters too close together and won't match up with the tank, and (2)...it leaks like a sieve! Both of these petcocks are leaking around the selector switch, because I believe the little round rubber gasket in there with the four holes in it is not sealing like it should. Is there a workaround or other solution to this problem? The OEM petcock's mounting hole are 20mm center to center, and I can't find anything with two hose barbs. There are a lot that Look like the OEM one, but I can't keep buying petcocks until I find one that works - does anybody know of any other petcock that works that doesn't cost $100?  Also, any tips on a new petcock or repair kit for a '79 KZ400H would be good to know too.

I am assuming it is the same petcock as used on the D model. If so, the packing (4-hole rubber) has been NOLA for some time. The common fix is to use the packing from an early CB750 in your original petcock.

First I do not have a 400 so have no first hand experience with the petcock in question.  I have found (on both Kawasaki and Partzilla) 2 different part numbers for the petcock 51023-051 and 51023-060 both of which appear to make use of the same part in question 92065-099. A quick search on line showed some ebay sellers claiming to have OEM ones.  I can not say if they do or not.