I have stumbled upon the notion of a $K$-valued Haar integral on a locally compact group, where $K$ is a non-Archimedean field, as well as the $K$-valued modular function, in an article of Schikhof. He cites his thesis "Non-archimedean harmonic analysis", but I have not been able to find that book anywhere. Is there any other more accessible reference where I could read about this? I am particularly interested in the $p$-adic case.
You will find it in the following link: