How do I go about getting a replacement wrist strap and lens cap for the OSMO?  I want the DJI branded items but CS couldnt help me.

You could use a OSMO 37MM adapter to turn the OSMO'S lens thread to a standard  37mm thread mount giving you a greater choice .Bit of an expensive work around but allows you the choice of lens caps,hoods, nd filters and dioptre close up lenses to name a few.Care should be taken in the choice of lens hoods as some may cause vignette.