B&H Eb Valve buttons?

[22sgw]

I managed to acquire a fully functioning 3 valve compensating B&H Eb imperial tuba (1977) from Ebay for ?100, it is in the repair shop now being cleaned and valves + slides being serviced. However, one of its valve buttons is not original, so you can push the valve down too far with it, I'm wondering if i can track down 1 imperial B&H tuba button. The original buttons are the ones with the faux-ivory looking white material set into them with a beveled ridge on the side of them (i haven't got a picture).