I rebuilt my engine with original Honda pistons but when the time comes I will probably put VHM pistons in as they are long out of production.

Some consumables are still available from Honda, .4mm and .6mm base gaskets are still available and the NSR base gaskets are .5mm and available, I bought pattern head O-rings from a place in Germany called gp-u-moto. They also sell Barnett clutch plates for the NF5, I plan to order a set of those so will let you know if they are any good.

Gasket guru in the UK makes all the gaskets as well but I prefer to use the Honda base gaskets for consistency.