Zinc plating of small parts like nuts & bolts is very easy to do at home with commonly available items and household "chemicals" (white wine vinegar, epsom salts, sugar). Especially if you already have a DC power pack from a model train set or something similar. The main problem is that only 2-3 items can be plated at one time, so it can be very time consuming. The other thing is that the results are only as good as the preparation of the part before plating. It must be clean and rust free which usually involves aggressive wire brushing and a short soak in phosphoric acid ("rust killer" available from hardware stores).
I've done most of the fasteners for my Healey and have actually written a short paper that I was going to submit to my local club's newsletter but never quite got around to.
If you have the time and the inclination PM me and I can send you a copy of the article.
JPF