Well one very dangerous thought would to cut the ac terminals very short AFTER soldering wires to them for the AC supply and connecting the DC out to your project. I've done it but I ALWAYS made a plexiglass case for the supply (Looked Real Good albeit a poor means of construction) workable though if PROPER SAFETY considerations were foremost in mind.
The 'Better thing" might be for you to search Ebay for the correct item or a combo that will work, a wall wart and an internal switcher either buck or boost as conditions require could be purchased inexpensively. I know because I Frequently shop there.
Personally I would recommend a 'Wall Wart" for 2 reasons, First You don't have to build and test it carefully before you use it... (Power Supplies tend to be Real Important). and Second, they are very easily replaceable. All it takes is a matching Jack for the PS chosen.
Doc