Does anyone have an 100amp alternator for JDM Gen II 3sgte? It has a round plug insert on the back.

Just had the same problem. The Aus retailers (autoelecs, super cheap, autobarn) all have the same part number but only at 80 amps. Nightmare was solved by rareelectrical (Amazon, eBay, shop in the USA).
$350 delivered in about 4 days.

Alternative you can buy an Aus supplier alternator and have it rewound for about $200 to the amps you want, but rewinding voids warranty and works out more expensive and longer.
Hope that helps,

Try a local auto electrician, find one that recondition alternators.
 
They will be able to rebuild yours, ie strip it down, clean it up, sandblast the aluminium housing, replace all bearing, brushes ect, put in lathe and machine the slip rings, if the reg is faulty replace that.
 
My parents / family ran an auto elec here in melb doing just that. If you have a genuine OEM Denso alternator, rebuilding it with genuine regs and good bearing ect will most cases be cheaper and better than an aftermarket / cheaper alternator or ones that have been rebuilt overseas.

Agree, check what's wrong with yours, my autoelec did it for a low fee (strip it and put it on the test bench).
The autoelec disagreed with rebuilding mine, recondition with a genuine parts at over $1400. I didn't believe the part costs so I checked with amayama and the parts are expensive or $2k for the alternator.
Yep I am happy the battery charges with what's possibly a cheap Chinese, I got what I paid for - something that charges the battery. Mates had there's rebuilt for $200, mine was a dead situations and fraction of the cost.....
Check what's wrong with yours and if it can be rebuilt cost effectively.

I have 1 available in Brisbane willing to freight $100 plus freight