E30 Zone

hi i have a problem with my horn. When i first had to remove the steering wheel from my e30 i somehow managed to lose that little carbon brush that sits in the sring! has anyone one got any ideas of what i can replace this with. would a smaller bit of any old metal do the trick? or does bmw sell the carbon brush. or any other ideas are welcome as i have the MOT coming up soon!
cheers

Carbon brush and holder should be about £4 from BMW (ask zimmerbimmer1 on here. His prices are delivered to your door), or ask for a used one in the 'e30 parts wanted' forum.