The ONLY one I know of, is Foremost Insurance - and you're NOT going to be charged the same rates as a house with updated wiring.
I'd suggest you make the wiring upgrade part of the sales deal, and make the old owner pay for it.
Keep in mind, knob & tube wiring is 1950's. Aluminum wiring came after THAT - so the WIRING in your house, is pushing 70 years old - which means it CANNOT safely handle current household electrical draws. There's not much "older" than knob and tube style.
Your idea of "reasonable" is what has to get adjusted - it's not "reasonable" for a house with 70 year old wiring, to be insurable at $90,000 for under $600. Or $800 either, probably.