Ohhh yes sir! Rob Webb, Rob Webb, Rob Webb, ROB WEBB! Edit: To clarify, drop Rob Webb an email and he can help you. I've had nothing but success with his mod chips.
I've modded lots of them. The biggest problem you have now is that there were a lot of subtle variations between the different Saturn models, and the modchips were being changed with each revision to add support - since a lot of the chips you find now are old, it's possible that you might get one that doesn't work in your particular machine or needs some special installation method (like running an extra wire to the CD drive clock). The other thing which you probably know, but has tripped up a few people that are used to the PSX, is that all the modchip does on a Saturn is to bypass the disk authentication - so it won't help you if you want to play original import discs, you need a separate mod (or an Action Replay cart) to do that.
You can play copies from any region with just a modchip, but you have to territory patch them (to Japan, in your case) first. The modchip won't let you play imported originals, since the main saturn BIOS is the thing that checks that. To bypass the region checks, you have a number of options: 1) Patch the image (obviously, this only works with a burnt disc) 2) Use something like a Gameshark / Action Reply that bypasses the checks 3) Add a territory switch to the main board so you can just switch select the one you want 4) Replace the BIOS with a modified version that has the territory checks removed. 1) has the problem that it only works with copies, 2) uses up your cart slot so if you want to run a game that uses something like a ROM cart and it's from a different territory you are stuck. 4) is probably the most convenient. There is a final issue, which is the video standard - your Japanese console is NTSC running at 60Hz, so it will have no problems running Japanese or US games, but some PAL games don't like the 480 line / 60Hz video format and run at the wrong speed and/or clip some lines from the display. So for a full feature modification you really want a 50/60Hz switch too. My personal preference is to implement this using a little MCU and a long press on the reset switch so that you don't have to make any external modifications to the console - but if this isn't an issue with you you can just drill a hole and install a little switch - the wiring is really simple.
Mine is Japanese too, ad said it has a modchip. Haven't yet gotten the bios chip I acquired installed.
Mixed bag of different types. LEE_02 (which appears to be 20 and 21 pin capable), SSIC7A, SSIC8B (green and blue PCBs), SS-08, SSB-02, EMSIC, EMSIC2, EMSIC6, EMSIC7, THOMAS?( 20 and 21 pin capable), STKEYA, GREY 20?, HK 1, and one or three others that don't have any clear designation on the PCB but are clearly of differing designs. Problem is not a one of these has been tested so far. Fun fact: almost all of them have the ability to be fitted with 20 pin connectors, if you can find them.
Be nice to find some of these 20 pin connectors as the vast majority of these chips just need the connector pads populated with nothing more added.
These ones should do the trick: http://www.digikey.ca/product-detail/en/HLW20S-2C7LF/609-1835-ND/1002150
If anyone was curious this is the complete list of 'named' chips I have: Thomas Gary 20 LEE_02 HK 1 EMSIC EMSIC2 EMSIC6 EMSIC7 SSIC7A SSIC8A SSIC8B SS003 SSB-02 SS-08 STKEYFA Guess I'll order a handful and give em a shot. Need more 20 pin ribbons though. These look like they might be good: http://www.digikey.com/product-detail/en/0210390363/WM10046-ND/376541
They work perfect, I used the exact same FFC when i was modding the SSIC8B to work with my model 1. http://www.segastyle.com/model1Alt.html If you scroll down to the bottom, near the end it shows "horizontal installation" and it shows which FFC cables work with the saturn and the 5" length one exactly matches the one you listed.
