toroid filters for pH probes?

[morty]

Anyone know the right size/type of filter to wrap a probe's cord thru to block EMI and promote stability in its reading? And a good place to find them?

[morty]

well no replies, I think I'll try this one

http://www.radioshack.com/product/index.jsp?productId=2103979&cp

but I may want a few more, so if anyone knows a cheaper source please chime in!