I don not think you have to worry that much about brand, model and build-year of a SCSI harddisk.
I used several sized in the past. I even used 32Gb 68 pins harddisk in the past with a 50-68 pin converter with a S3000XL, S3200XL, ASR-X etc and never bough/usedt a harddisk that did not work.
Personally I would look for a 500 MB or 1 GB 50 Pins SCSi harddisk in your situation. The Syquest is 135 MB. This is pretty small.
I have a 500MB disk and a 2 GB disk at home somewhere as back-up. I will have a look for the brand and model number and will post later.
Cheers