It looks like 5 1/4” drives themselves are getting quite rare, not many on eBay, while there are lots of 3.5”. So even with a controller, getting a drive is not

It looks like 5 1/4” drives themselves are getting quite rare, not many on eBay, while there are lots of 3.5”. So even with a controller, getting a drive is not simple. I’d say the main reason, is that 3.5” drives are much more common, and they overlapped USB They are much more standard than 5 1/4” drives too.