There are converters (look physically like a 3.5 hdd) for 2.5 inch drives which can be inserted next into 3.5 slots (some with easy loading for the 2.5 inch inside without using screws). Once inserted you can use it like a 3.5 inch HDD anywhere using any mounting. Bought a pair of those myself. Got an aluminium one (IB2535 series) from ICY Box for good cooling.