Pure solid silver wire

My recommendation is, don't.

But if you're determined I got mine from Audio Consulting.

Please note: having done that, is why I recommend not doing that.

agreed, silver is not a good option for anything, in my opinion.  That being said, if you are looking for internal wiring (inside the power strip) to connect the actual outlets, Tempo Electric sells solid-core silver wire even at 12awg and 10awg sizes:

http://www.tempoelectric.com/cables_DIY.htm

If you are looking for a power cord, there are probably a few out there.  A couple I do know about are Wire World Platinum Electra and Purist Audio Design Diamond Limited Edition. 

Rio Grande .999 dead soft annealed silver round or flat wire sounds great.  Bundle 20awg strands as needed to make your total gauge. Commodity prices; order on-line.

I'm using this: http://www.audiocadabra.com/blog/audiocadabra-ultimus-12-awg-2-00mm-solid-silver-wires/