When you say total nav loss, I assume you mean traditional nav aids as well. I routinely navigate in Canada's high arctic. With total nav failure by day if you had the capability to convert your instruments to true, point the aircraft at the sun, then 15 x GMT-west long will give you your true heading. Arctic radio will then have you on radar and I'm sure would be able to provide vectors to a suitable airport for nav repair. I hope this makes sense, I do fly a pressurized aircraft, but am not a high flyer so hopefully I was able to help. We also always carry an astro-compass.