# Reference for $p$-adic Haar integral

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.