Hi, there are lots of singap out there with initials of various Javanese kings embroidered/sequinned on them, not the least HB X. I have at seen at one particular shop half a dozen of such singaps, so don't place too high hopes on them.
And on Javanese kerises, especially the pendok, one often sees the royal insignia engraved at the back, and I'm quite certain the kerises had nothing to do with the kraton.