Yes, Iomega eventually licensed disk production to a few other companies. I know for sure that Maxell and Verbatim made them, and Wikipedia says that Toshiba,

Yes, Iomega eventually licensed disk production to a few other companies. I know for sure that Maxell and Verbatim made them, and Wikipedia says that Toshiba, Fuji, Epson and NEC also produced some. When they were originally released, I believe the first model was SCSI-only and cost $199. Disks were $20 each and held 100MB. Eventually the price of disks dropped a bit, until they were around $11 or so in multipacks the last time I bought any. They also had backwards compatible 250 and 750 MB drives, but I don't know how well they ever sold. I never saw either in person. I think by the time they hit the market CD-R drives and media had dropped in price so much that Zip disks weren't economical as either a backup or file-transfer media.