Unfortunately, no. If I did, I would have bought another one by now and be done with it. I pretty much live in Den Den towh (Nippombashi) Osaka, and I know everyone in all the game shops. None of them have ever modded a console or even seen a modded console (any type, not just XB). MODs are ultra rare here.
I think the reason for this is two fold. One is that there is basically no need. Usually gamers awant a MOD to either play imports or play pirate copies. Japanese have no real reason to play imports, they get all the software first anyway (and can read the language), and the presence of re-sale (read used) software shops makes the effort to pirate copies unatractive. In the US major chains are only just starting to handle used software, but in Japan it's been going on since the days of the Famicom (NES). You also don't get quite as gouged by these shops as you do by the ones in the US. You can buy a game brand new, take it home for the weekend, and bring it back to one of these shops and get within a few hundered yen of what you paid for it. It's like renting!
The other reason is that Japanese regulations on MODs and equiptment to MOD are VERY strick (always siding with large companies since Japanese government is driven mostly by who bribed who the most, and your average Japanese is just a sheep being led to slaughter.). I think I would probably go to jail just for the stuff I brought with me from the US. It's not contraband, but the penalty would probably be just as severe. Don't tell anyone, ok?
After having said that, I would still like to reiterate my willingness to help in any way I can to forward the effort of making the save game exploits work on Japanese versions of software. If you are involved in this effort please contact me.
Thanks again,
J