Power cable for REL sub -- modestly priced

Does anyone have a suggestion for a longer cord for a REL 328 sub? It has a class D amp.
Before you suggest high dollar cords, please know that I'm not a skeptic, but am tapped out for power cords. And, for what it's worth, I had a Pangea AC9 1 meter power cord which I experimented with using my REL. Made zero difference. In fact, in an exchange with REL, they said this: "A while back, REL tested some third party power cords with our subs but did not find a noticeable impact."

So, my question is about a decently made but not pricey brand of extension cord for a REL sub. I'm not looking for Shunyata etc.  Any suggestions? Thanks.