2.5" to 3.5" Hard Drive Tray Holder for PCI SSD HDD Metal Mounting Steel Bracket Adapter Black

https://a.co/d/0jaMaeR0 That's for a pcie slot. But you could modify it to remove the pcie bracket and screw to the case then mount the HDD to it. I also saw 5.25 mounts that hold either size drive and could be adapted to use. Perhaps a drive sled for a removable drive could be used. Some have mounts on bottom for 2.5 and sides for 3.5.