I suppose if you are in a real bind that you could cut the ends of a test lead set that's rated 600V or higher. It'd be expensive as all get out to cut the leads on my Fluke T5-1000 but they are rated 1000V.
I have about 30' of Locomotive wire that's rated 1200VDC (Lots of rubberish insulation, not so much wire) from Boeing Surplus back in the mid 90's. . I miss that store.