I sell bags of assorted used tubes when the time comes to clear out if you want me to give you a shout next time. All used but usually 20 tubes for 20£ sort of thing on FB marketplace. Shipping may be the killer though as they aren’t light
I don't have a set ake but buy in bulk ftom 3bay with water make seems best value for money at the time, never had an issue with punctures yet(touch wood)