UD-18A Head Gasket

I have recently aquired a UD-18 57 KVA generator plant and are in need of some parts.
The head gasket appears to be leaking.
I drained over 18 liters of water out of the sump.
It has a broken rocker and several others have broken in the past and been welded up.
It appears whoever maintained it didn't quite know what they were doing. Some tappets were loose nough to fit a finger in and some were tight. Probaply the cuase of multiple broken rockers. Several push rods are bent.
Despite this when we turned it over to check the rockers it fired.
We have since pulled the head and now want new gaskets to replace the leaking ones.

Can anyone point me in the right direction to find a UD-18A head gasket supplier. I am need of some local knowledge that I don't have for suppliers.
Please keep in mind this would have to be an internation mail order parts supplier as the engine is in New Zealand.

For interest sake photos at:
Link

Thanks,

James

But first I need to fix the stripped timming idler gear.
I'm on the track of some TD-14 parts near me locally which I belive is the same part accoroding to my parts book.