Okay, found it! For simplicity, I will copy/paste it all here:
COMPLETE POLYSICS MEMBER LIST
1. Hayashi Hiroyuki, 1997-present. Born August 8, 1978. He is an original member of Polysics and he came up with the idea of he band after watching a Devo music video. Fresh out of high school, he started Polysics with some of his classmates. He is the guitarist, singer, and programmer of the band and the first Polysics live was on 3/4/97. Hiro is a ball of energy on stage and is constantly moving and interacting with the crowd. In the first years of the band, his stage name was POLY1.
2. Makoto Kawabe, 1997. An original member of Polysics who left the band after the 4/14/97 show (roughly a month after the first Polysics live). Not much is known about him or what he did in the band.
3. Kaneko Shingo, 1997. An original member of Polysics who left the band in 11/97. He was the first keyboardist of Polysics, and was later replaced by Kayo in 3/98.
4. Sako Eisuke, 1997-1999. An original member of Polysics who left the band in 5/99, only three months after 1st P was released. He is credited with the keyboard, vocoder, and throwing bread during concerts. He is seen in the Plus Chicker PV, and in all live performances known of him, he is very energetic and looks very crazy. His stage name was POLY2.
5. Kayo, 1998-2010. Born March 27, 1979. After seeing some of their live shows, Kayo was approached by former classmate Hiro and joined the band in 3/98. She was the keyboardist and left the band in 3/10. Her first live show was on 3/3/98. Her on stage persona was that of a robot and her image became very iconic for the band. She sang countless songs and her pleasant voice was a great contrast to Hiro and Fumi's strong voices. In the first years of the band, her stage name was POLY3.
6. Sugai Junichi, 1998-2003. Born September 6, 1975. He was a drummer in the band and joined 4/98. He left around the time the Kaja Kaja Goo EP was released (5/03), and it is believed that he did not like the direction the band was going in. In the first years of the band, his stage name was POLY4.
7. Fumi Mutou [last name uncomfirmed], 1999-present. Born April 25, 1978. In 6/99, Fumi was invited by Hiro to be the support bassist of the band during live shows, even though at the time she a guitarist of a band called 54NUDE HONEYS. She participated in the Neu album in 2000 and then was made an official member in 6/01. Her first live show was 6/29/99. While Hiro does some crazy bit of jumping jacks or crowd surfing, Fumi keeps up the melody with her amazing bass. She is almost a second leader after Hiro, as she helps write and compose songs and even talks just as much as him during interviews.
8. Ishimaru Kazuyuki, 2003-2004. Born November 4, 1973. After Sugai left the band in 2003, Ishimaru was the support drummer and filled in for the drums until Yano joined the band the following year. He is currently a member of a Japanese band called SNAIL RAMP, and was still a part of that band during his year with Polysics.
9. Yano Masashi, 2004-present. Born June 6, 1981. Starting on 5/30/04, Polysics did a seven day concert set where each day represented a different album, and during these lives they also wore the corresponding outfits for each time period. This event was the first time they announced their new drummer who had auditioned for the spot. Yano's tight sound on the drums really speed songs up, which has became very apparent in the newer albums.
So basically, Polysics was founded by Hiro, Sako, Kaneko and Makoto in 1997.
Then Makoto left a month after their first live.
Kaneko left at the end of 1997.
Kayo and Sugai joined early 1998, making the lineup Hiro, Sako, Kayo and Sugai.
Then Sako left mid 1999.
Fumi joined a month after Sako left, making the lineup Hiro, Kayo, Sugai and Fumi.
They stuck with this lineup until 2003 when Sugai left the band.
Ishimaru was a support drummer for a year between Sugai leaving and Yano joining the band.
Yano joined in 2004, making the lineup we knew and loved so much: Hiro, Kayo, Fumi and Yano.
Kayo left the band in 2010, leaving the lineup as a trio of Hiro, Fumi and Yano.
In the original entry on NBB.com, I had listed some of the sources for this, but mostly, the Absolute POLYSICS book was a godsend with all the concert tour dates. I got a lot of other information from various online interviews.
I don't post here much anymore but I still have a fond appreciation for Polysics. Hit me up on Twitter @west_haven if you really wanna talk to me