Translation and transcription for a tattoo, Khuzdul/Cirth

[Elendil]

You must use the KH letter. As well as using the TH pour Thorin.

I am sorry to disagree, but the question is very relevant. Based on the Angerthas Moria description, I would personally use the KH rune, but in using this mode for the Khuzdul inscription on Balin's tomb, Tolkien used the combination K + H to represent the kh in Uzbadkhazaddûmu. See reproduction and transcription here.

So at least for Khuzdul, this seems to be the most authentic way to represent kh. This actually ties back to an interesting theory by Magnus Åberg on this sound in Khuzdul (see his analysis here in French; there's a link to the English original in the links at the bottom of the page).