David - Thank you - there are indeed stacks of information about staining keris on the forum. I recall the sulphur and rice water method but I'll probably put this last on the list because I don't want to come home to my housemates gathered in a circle, dressed in hazmat suits, talking about how best to evict me

I'll ask and look around to see where I could buy some realgar. I don't suppose I'd need too much to stain a single blade? (well, assuming that the first job is a good job, which seems unlikely).
Alan - Gotchya - thanks. In another thread from some time back you mentioned using cold blue to touch up some blades and rifles, and that while you hadn't used it to stain a complete blade, it is possible that cold blue could do the job. Have you since attempted this?
To all - Ferric Chloride gets mentioned a lot in my research into etching and staining. Would using FeCl likely give me a better result than fruit or acetic acids?