Dont know a good source of LMR400, i found one place that was about $6/meter in CHC, with free shipping on orders NZ$100+
N connectors you can get from dick smith NZ$4
RP-TNC you can make with a BNC T Connector, regular TNC, and a hacksaw. It's quite easy really, but not all BNC Ts are suitable.
Worked a treat for my aironet card which uses RP-TNC, the best source i found for factory made RP-TNC wanted like NZ$60 each (they were a cisco part so i guess you have to pay $50 extra for the brandname)