I think you could rely on online social networking sites, I don't know which ones are best for people living in Japan... If Japanese girls can meet gaijin through these sites then surely gaijin can meet gaijin... You might even try posting on Craigslist, but as usual, I offer up a bit of caution when meeting people online, always keep yourself safe by not giving out any information until you feel comfortable the other person isn't a creep.
A long time ago people thought meeting others online was weird and anti-social, now it's more accepted, if not simply ubiquitous---- it's just that with social networking sites, they know what type of music you listen to before they meet you.
You can also go where other gaijin go to hang out, look through the magazine Metropolis (It's online, and free), it holds several parties a year, and from the pictures there are many many gaijin thre as well as Japanese, which I think is a great combination...
It will also keep you clear of the grim confines of places like Gas Panic, which though now is simply a haven of awkward Eikaiwa teachers looking to meet easy Japanese girls, it still seems to have this legendary mythology to it... but you wouldn't be interested in a place like that anyways!
ps. I also remember you!