I love the arbites and their Judge Dredd vibe.
Luckily when Steve Buddle sculpted the excellent Adeptus Arbites Judge, he included a few head variants. All three alternative heads are great, but my favourite is the ‘judge dredd’ inspired version wearing a helmet.
Other than the official arbite model, there are a few other manufacturers with minis that can be appropriated to 40k. Ares Mythologic released various minis for their Dark World range. Their Captain Jhonn Creek is a great fit as an arbite, though all the models in this range are larger than the 54mm advertised. I had to cut the figure down in the midriff so the figure can be the right height (quite laborious as the mini is metal).
Another suitable figure is from Wild House miniatures (now defunct). They had a great mini of a sci-fi armoured Officer (originally called Human Mal TAC Officer by Badsmile Miniatures).
Northstar models also have a few 54mm minis (often in the style of Mass Effect) that may also be suitable.