SGI parts and RS/6000 disk mounting (still)

Does anyone know of somewhere to get old SGI parts? I'm still looking for something with a R3010 on it for my 4D/25 (IP10/12 board or similar . . .). Most places (Reputable) seem to not have anything older than I2/Indy (and seem a bit pricy- but I guess that comes from having to keep an inventory etc.) (2) I'm still trying to figure out mounting the HDD in my 3CT. I looked at the IBM manuals, and they all seemed to reference the SCSI extender card (as used on my 370), but that won't fit in the 3CT. It's one of the ones with the two externally accessible 5.25" bays and the floppy mounted on top. It looks like some sort of drive rails, but I don't see the screw hole for securing the drive. I've got the drive loose in the cage, and it might have to stay that way, but it would be nice to know how it was really mounted.