What are those rubber caps called?

[Taipan]

What are the little rubber caps called that fit on where you would attach a carbtune to balance the TBs? Each TB has one of these and you pull them off to attach your carbtune?
I'm trying without success, to find them on the motobins website. Anyone got a part number for them?
Many thanks

 

[littleredrooster]

Throttle body blanking plugs?

About 23p each, IIRC