there are a few options out there. If you want to buy one, just google it. IMO you would be better off finding an alternator shop that does rebuilds, etc. especially a shop that does work with heavy equiptment, big trucks, ambulances, etc...vehicles that require high output alternators. they will have experience in rebuilding your current alternator to high output if possible. they just crack it open, replace the internals, and rewind it to a higher output.
example...I've had 2 or 3 done since the mid 90's at a local shop here (too bad your in cali). The last one was in a gm car that i believe was 70a and they wound it up to a bit more than 150a (more than enough) installed it, upgraded all the wiring, everything...i want to say it was $200 or $250 ish. keep in mind that was probably 5 years ago or better and prices will be all over the boards. nice thing about doing it with a local shop is they will more than likely stand by their work.
things to keep in mind...
how much current is your amp (or amps) ACTUALLY pulling???
2000 watts is vague...is that an rms measurement??
What a shop will do is hook your car up to thier magic box and determine how many amps your alternator actually needs to produce with your system turned up to its full potential, air running, lights on etc...Im sure you will need an upgrade but it may not be as big of a deal as it sounds.
Even with an alternator upgrade, i would still use a good cap.