vespa PK seat.

Need some advice on PK small frame seats and locks if anyone can help?

I have a 1992 PK 100 XL which has a broken seat lock.  The locks on the sip website are all different to mine and I cant seem to find a new lock or a new barrel to fit it.  My catch has four bolts at each corner and the lock slides along when pushed in to engage the catch and push it forwards.  It is appreciably longer and different to any of the locks and barrels pictured on the sip site.  There are a couple of locks not pictured but the description is pretty poor and I don't want to order a lock that isn't any good.  

 

This is what the lock barrel and casing look like. Any ideas which one I need to order from the SIP site?

Also I did consider, and still am, getting a replacement seat.  However I can only see one seat on the SIP site that has a hinge plate like mine. Mine has four bolts and the hinge is U shaped to fit either side of the plastic small tool box.  Most of the seats I have looked at and would like only have a hinge with two bolts and the hinge is a square shaped small plate not a U shape hinge.  Would these still fit mine?  i.e. are the two bolt holes in the hinge the same distance as the first two bolt holes on the U shaped hinged seats?  Hope all this makes sense.

About the hinge, I suppose you could make some kind of "adapter" with a thick enough metal plate. But if you chose the correct seat for your model on the store, it should be no problem.

When I ordered a luggage carrier, I used all the washers and nuts I wanted, and it set right, even with some size differences.