A "wall-wart" is definitely a good, safe possibility. However, if the original poster does not wish to use a "wall-wart" (and there are definitely legitimate reasons for not wanting to), an OEM power supply module might be a great choice. There are a variety of players in this market, not the least of which are Power-One and Astrodyne. Astrodyne's Ultraminature Modular Switching line caught my eye; they are quite small, self-contained solutions that carry a variety of regulatory approvals. These, too, however, are not without their caveats. As Terry pointed out below, just brining 220V into your enclosure complicates things significantly.

Still, all things considered, with so many power supply products on the market, designing a custom one without an extremely compelling reason to do so sounds a lot like reinventing the wheel. More often than not, that's a bad engineering decision, as the result is often inferior in some way, perhaps in safety, reliability, cost effectiveness, or some other metric.

--Sasha Jevtic