Aftermarket drive enclosures have been made by Chinese ODMs going back the the SCSI days, and the back pages of MacUser and Macworld.
The vendors like APS, Granite Digital, etc. just have their names screened on them.
Some, like APS, did go a little farther and commission their own designs, and develop companion software utilities, like OWC does now, but they don't manufacture hardware.
The advantages of "rolling your own" have largely gone away, and the market has shrunken to reflect that. The cost of turnkey drives from the big brand names is lower than the total cost of a bare drive plus an enclosure. And while they're not great enclosures, they do the job.
The storage enthusaists who still roll are now into NAS and multi-bay RAID enclosures, not single bays, so there are fewer choices.
Without knowing the specifics of the desired solution, it's not possible to make any recommendations.
