Seat with a pin type latch??

Buddy of mine has 74 900 and seat that came on the bike does not latch. Obviously not the proper seat. His seat has the squared up U shaped latch and his bike has the lockin system for the pin style that catches a couple inches on the inside part of the frame. Anybody know what I'm talking about and know where i can find this kind of seat?

www.z1enterprises.com/detail.aspx?ID=2610

I suspect that this is the seat w/correct hardware that he needs.

Hey thanks alot man. I just sent ol boy the link so he can do work. Much appreciated!

HEY I have just the opposite problem. My SEAT has the plunger type on it, and the FRAME has the rectagular latch.
Its my understanding that 73-75 used the round funnel type of plunger and everything there after uses the rectangular style. Anyone know where I can get the female plunger [part on the frame] style ? Right now theres a new one on E-bay but it has no lock as well as its already over 30 bucks, 30 isn't the issue I don't know if the later mdl. locks will interchange? And it appears you need a lock to make it function correctly. Or it will just sit in the hole and thats it.
Anyone have any info on ythis ? Parts supplier etc.
I have been looking on and off dfor a year with no good results.
Thanks Ahead of time !
Ed