Speedo bulb for sprint velose

Hi, I'm trying to find a speedo bulb for my replacement speedo. I can't seem to find one anywhere, and it's  difficult to find the right size ( see pic)

The bulb should go in that top left hole, and it's about 9mm in diameter, and at some point it must have a rubber grommit of sorts! Does anyone know where to get hold of one??

Regards Lou

hi ....

normaly it has to be the 6v 1,2 W

item code 575114