I have an ancient PATA enclosure, almost 10 years old with FW port that I opened up and modified to take two drives several years ago. I then added a PATA/SATA convertor last year so that it now takes SATA drives.
So there you have it. SATA -> PATA -> Firewire.
Last week my Time Capsule died, so I just dug it out of the garage a few hours ago to take over my TM backups while I sort out my dead TC with Apple.
You can get empty externals pretty cheap if you look on the net. USB ones are dirt cheap. PATA / FW ones are cheap. SATA / FW ones were a bit more last time I looked. 2.5inch SATA / FW enclosures were rare and pricy last time I looked. I really wanted one at the time as the FW carried more juice and was faster than the USB connection.
BTW TM over Firewire absolutely rocks. Zero to full backup in a couple of hours, while with TC over gigabit ethernet was an overnight job.