6800 Volt mod question?

[Section8]

So I went to the local electronics store to get a Variable 100K Ohm Resistor to do this mod but they didn't have any. Can someone please provide a direct link to one that will work for me. I looked on the internet but there are like thousands of them and I am not sure what one would work best for this application. This is the mod I am talking about here:

http://www.vr-zone.com/index.cgi?i=926&s=1

Thanks...