A question for chemists

One of the nuisances of being an educational technician is the way that many products aimed purely at schools have incredibly high prices. Case in point is a kit of chemicals used to simulate blood group testing which costs 40-odd pounds for a total of about 100ml of various solutions, all of which I suspect are fairly basic compounds. What you get is vials of "antibody A", "Antibody B", and (in the deluxe kit that costs much more) "anti-Rh", some samples of fake blood, plus a few mixing sticks and bits of laminated card to mix them on. I suspect I could make the lot for a pound or two if I knew what the chemicals were. The type A blood clots when mixed with Antibody A, type B with antibody B, AB with both, O with neither, and so forth.

Needless to say the chemicals are not identified, and in any case I would prefer to develop something independently and publish it on the web without having to worry about the manufacturer saying that I've ripped off their product.

So what I need is three distinct blood chemicals, each producing a precipitate when mixed with the appropriate "antibody", but not precipitating when mixed with each other or the other "antibodies". Harmlessness would be a plus, and they need to be miscable with food dye and water to look vaguely like blood. The precipates should look like little blobs of clotting if possible.

Any suggestions? Or anyone know of a web site I've missed that describes a suitable set of chemicals?