you shold get the gasket from any motor factors, you get one in a head set but there like £20, but you get every gasket for the whole head inc the head gasketso not really that bad.
I bought an inlet manifold gaskit from nissan dealers in febuary this year; £9.50 inc. VAT.
Thermostat housing gaskit (and that's the complete housing that the distributor slots into not the little triangle piece); £4.49
Rocker cover gaskit; £7.97
Timing Belt; £26.46
Everthing arrived the very next day.
Have you tried your local scrapyard they could have your parts & any other parts that you are after or you can try these guys for your Nissan Car Parts thats were i go if i need any parts for my car.