Inside trouser Holster 890-232, and Double Magazine Case 831-1.
They are available in black and chestnut brown (shown) Mag cases available in belt loop or paddle style (shown)
I got both for less than $50 together delivered on closeout.
3 mags of 6 may not seem like much these days, but back in the day of wheelguns, that was how many rounds we carried on duty.
The idea was to make each round count. Still works for me.