Thank you for looking into this, thingstodo!
FWIW, I did some digging for a cable that would meet the specs you provided, and found something at Mouser: ( I really don't need 1000 ft of the stuff )
6459 OR005 Alpha Wire | Mouser
Unfortunately, they didn't have a data sheet.
According to Mouser's info, It's an 18g shielded single twisted pair wire good for 600V.
I only need 1 pair, so this works out pretty well for me. Also, it's in 100ft spools which only cost about 60 bucks.
***edit*** I looked into it at Alpha wire's website. The wire is also only good for 300V.
However, for a bit more, this one fits the bill: (600V, but the wire gage is 20AWG)
5616B2001 BK005 Alpha Wire | Mouser
- E*clipse