RCA Phono Interconnect Under $400

RCA to RCA.  Since money is an object I'll have a look at the used cable store.

Here ya go!

If the cable does not have a ground, you can just make one. 

An RCA to RCA cable will definitely carry audio ground. If the tonearm or TT need ground to the phono, any old wire will do.

when I bought my long tonearm, the maker essentially insisted I buy this Ortofon

I did, but frankly I do not hear any difference comparing several, including inexpensive one, Acos Lustre's OEM or Custom Pine Tree cable I had made.

I would say, buy from a source that accepts returns, try, keep or return.