Years ago I would have reached for Ektar 1000 or even better a fast tungten balanced film. After a quick look at a couple of mail-order suppliers I could find no tungsten films and nothing faster than 800. Trouble is, if it is daylight film then by the time you've bunged a filter or two on the front you've lost even more...
Has all the fast stuff gone, now?
No, thank God all the fast color film has not gone away. Granted the ISO 3200 film is no longer around, but there are plenty of current ISO 800 and ISO 1600 options in color neg. Also, there are color slide films at ISO 200 and 400. Both the slide films and the neg films can be push processed to increase the speed if you can find a lab who will do it for you. The negative films should be overexposed in low light by a stop (or more when pushed). Even the slide films do well with slight overexposure (+1/3 to 2/3 stop only when pushed).
As for Kodak Portra 800: It's the current "version" of Ektar 1000. In fact, both have/had about the same ISO. Ektar wasn't really a 1000 speed film, and/or Portra is faster than a real ISO 800 film.
There is also Fuji 1600...a great film for rock concerts if I may say so myself. I consider it the color version of the Kodak P3200. If you like P3200, and liked Ektar 1000, you will probably like the Fuji 1600. Ditto for the Kodak Portra 800.
For rock concerts, I recommend the following:
-Portra 800 @ EI 640 (but you need a very wide aperture)
-Portra 800 rated at EI 1600 and push-processed 1.5 stops
-Portra 800 rated at EI 3200 and push-processed 3.5 stops
-Fuji 1600 rated at EI 1000 and processed normally
-Fuji 1600 rated at EI 2000 and push-processed 1 stop
-Fuji 1600 rated at EI 3200 and push-processed 2 stops
-Kodak E200 or Elite Chrome 200 rated at EI 1000 and push-processed 3 stops
-Fuji Provia 400X rated at EI 800 and push-processed 1.3 stops
-Fuji Provia 400X rated at EI 1600 and push-processed 2.75 stops
For mixed lighting, Fuji 800Z may do better, but I have not tried pushing it yet. It will probably behave similarly to the Kodak Portra 800 when pushed.