Probably most old 50 pins SCSI harddisks will work with the S1000. The sampler will only reconize/format 512 MB if the disk is larger.
Last week I build a SCSI Cf reader/writer) with the AKAI IB ID2SC SCSI-IDE interface with a standard IDE card reader attched to it. The AKAI SCSI-IDE interface is designed for the S5000/S600, but wotks perfect (format/read and write) with my S1100 (and S3200XL and Ensoniq ASR-X)
Cheers