Seat Belt Clip Part Nos

Could someone maybe tell me where I can find out what the part number
would be for the little bits of plastic on a Defender 110 seat belt,
that is supposed to keep the metal seat belt clip from sliding all the
way down the actual belt ?

Its been driving me crazy for weeks now, and everytime I get into the
landrover I have to struggle to retrieve the metal seat belt clip from
the bottom of the belt, where it gets jammed in against the door.

Im sure its something simple but I just need to have some way to keep
the metal clip half way up the seat belt like any normal car.

Thanks for any assistance.