New valves have come without them, any idea where I can pick some up?

Or has anyone had any luck bodging with bits of inner tube?

Plumber’s merchant. Proper one, not a diy shed.

They come with o-rings?

Where do the O-rings go then?

Some valves come with them to go on the outside. Which makes absolutely no sense because the rim should be airtight, and no matter what you do with the outside of the valve, the spokeholes aren’t airtight anyway.

(I think some rim strips have one that’s supposed to go on the inside to interface with the rim strip- but I’ve never seen one)

Ghetto tubeless I did I needed to put something in the outside. I just made one from bit of inner tube. Without it the sealant wouldn’t seal. Despite a seemingly good seal from the rubber around the valve inside. Could be the rim strip I did (heavy duty tape stuff) was letting air under it round there. No problems with the spoke holes though. I had the same problem in both front and rear wheel.

The valves with my CB tubeless wheels came with o-rings. The Stans I think don’t, but seal fine.

One argument for o-rings is if the nut comes loose the valve could push into the rim and the seal inside is broken, but the o-ring outside might stay in place, holding the seal and/or keeping the valve from slipping. Maybe.

In theory they might not be necessary but in practice they seem to sometimes make the difference between success and frustrating failure. Did on my most-recent conversion anyway.

Plumber’s merchant. Proper one, not a diy shed.

Thanks, will investigate.