what i ment john was with exstinguishers u get the nut and the stem with an o ring- normally all in stainless... otherwise google co2 regulator stem and you'll find this sorta thing;

http://www.wecs-ltd.co.uk/index.php?pag ... 6&vmcchk=1

otherwise.. im not sure but i imagine theres a few adaptors out there for nitrous kits availible that take the gas thread to a BSP size...i imagine nitrous bottles are the same thread as co2