The only way I'm aware of to find Int'l regs it to find someone with an ACARS log set up for the area you likely flew over. There are a few really good ones out there, but it's really hit or miss. That said, I have every reg (except a couple) I've been on for the past few years (over 100). I also keep track of the Out/Off/On/In times and mileages in my spreadsheet. It makes for some nice charts and such (keep track of average block and flight times). It's kinda weird when you realize you were just on the exact same aircraft last month between two entirely different cities (or the same ones for that matter).

dan