Air Valve

No wonder I have been unhappy with the way my S2R is handling, the bikes got a defective air valve in its front wheel, its not resealing when I pull the air line off when trying to set front wheel tire pressure, I have to put a few pounds extra in and quickly poke at the pin in the air valve with my ignition key to try to stop it blowing all the air out and get it to seal itself. The bikes got Marchesini wheels and it looks like the air valve simply unwinds out of the wheel rim, can I buy one of these from any motorcycle dealership? Are they the same thing on all bikes from Addler to Zundap (well Hondas actualy cuz there’s a Honda dealer in my home town) or do I trek on over to JHP in Coventry tomorrow morning? Ty in advance for help ppl.