Best Alternatives to Black Gate Caps

Does anyone have an idea as to the best cap alternative to the Black Gates that are no longer available?

Specifically 3.3uf 50 Volt.
Parts Connexion still lists a 3.3uF, 50V PK Black Gate on their site(click on Black Gate, bottom of page). ( I wish Sanyo would produce their OS-CONs in higher voltages.
Try Nichicon's
KZ is the "top" Nichicon audio cap, but not available in 3.3uF. I would fall back on the FG or the ES (which is bi or nonpolar). Odyssey Audio uses ES series for their "upgraded parts" amps.
Michael Percy still appears to have these PK 3.3uF 50V BGs.