Well the CA870's closest match is the Remington 870 breeching shotgun. It's more or less a cut down pistol gripped shotgun.
For gear depends on what you like. Your WW2 kit is nice, perhaps build yourself a modern outfit. The breeching shotgun may work well with a Swat kit which are pretty easy to build up. Black/Navy Bdus, Pasgt Helmet, and one of the many many vests that float around here.
Or make something unique. I think a nice long black trenchcoat, an underslung holster for the shotgun and maybe also a shoulder holster for a sidearm, some sunglasses and you've got a pretty easily done assassin.
Your choice :-)
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