Although I've never used a DP-51 or tried this, S&W 59-series mags are widely reported to work in the pistol, although they project below the grip slightly. This is a BIG PLUS, as genuine OEM DP-51 mags can be hard to come by, although they're generally not too expensive when available. OTOH the S&W mags are typically plentiful AND cheap just about everywhere.
DP-51 mags are too short to fit in a S&W 59-series (59, x59, 59xx, or 91x), although it's been theorized that they would probably work in the shorter 69-series.
FWIW although the trigger system is almost entirely different, the S&W 59-series apparently served as a design template for the Daewoo DP-series pistols; they're almost exactly the same shape, they lock up the same way, most of the field-stripping procedure is the same, and 59-series holsters can often be used in addition to mags. However, the Daewoo trigger guard is more similar in shape to the squared S&W trigger guard used from the mid 1980's to the late 1990's, so I suspect you may have trouble with some S&W holsters designed for the much more svelte rounded trigger guard used on the earlier and later pistols. This is a well-known issue with the Smiths, so many holster makers list which trigger guard the holster is designed to fit.