What histological stain can I use for beta-keratin?
Not sure if this is what you are looking for, but I did some searching around for histochemicals and reptilia.  I did come across a paper by L Alibardi, Dipartimento di Biologia evoluzionistica e sperimentale, University of Bologna, Bologna, Italy.  Now, that exact application doesn't seem to answer your question, it did open up a web page that contained numerous papers on reptilia and their beta-keratin structure and investigations into that (citations of the original paper, as well as papers by the same author).  I didn't see any that specifically spoke to the exact stain used, but then this is a little outside my area of expertise.  Perhaps this link will give you an avenue to pursue?

Wish I could help more.