Good news, I found it on a Chinese site (here, links to Baidu here). I can't guarantee this is the same file soneek uploaded, but it looks legit. Here's an IPFS mirror: Pokemon Rumble MIDI + SF2.7z
It seems like the files are legit, and just from playing a few of them, they sound accurate too. I can't tell you how long I've been looking for these, so I'm glad someone else found them. These were exactly what I've been looking for. Thanks!