Why new ones ?
Can't you clean them ?
No. They're probably not dirty but gone.
37 years....
I totally agree with Speleo. Don't get the standard stuff (IF they already fit, I think the one you mention Etienne might be metric sized ?)
Those potmeters are expensive for a reason. David at RAM controls sells an even better quality than what Atari put in the SW yoke....
I haven't been into the loop about David lately but I assume he is in one of his hibernation-periods again ?
You could maybe try my old SW pots Ully BUT the thing is that SW's software is averaging out the potmeters during play (yes really) so that (temporary) errors (like jittering is) won't be (very) noticeable in the game.
So, my old pots may still be OK but may also not...