I don't have any great suggestions on this, other than to look on Ebay or Craigslist or your local fleamarket for a vintage home audio EQ deck.
Back in the 70's, this kind of thing was fairly commonplace. But they're much harder to find now. Behringer makes a little inexpensive 9-band desktop EQ, called the MiniFBQ800. But I'm not sure if it'd deliver the type of quality you want.
The next best solution is probably a mixer with a graphic EQ built-in. But they may run into a few more $$ to get something decent, that's noise and distortion-free. And you will generally only find features like that now on the larger, more expensive models, because the lower-end stuff is going more towards digital effects.
There are also rack-mountable graphic EQs, like the DBX 215s and 231s. But they are generally designed more for +4 dBu pro audio than the -10 dBV consumer audio that your gear is probably using. And have separate EQ controls for both channels, unlike the Behringer MiniFBQ.