I've bought a bunch of cheapest CompactFlash to IDE adapters I could find and designed a 3.5" bay adapter for it, to make it look similar to a 3.5" floppy drive.

The adapter board can be friction fit to the print.

There is a cutout for a 3mm activity LED that could be connected to the LED on the adapter board, however I didn't test this.

For best quality, print the model with the front flat on the bed and without any support material.