Here are some links to some standard gear. I tried to indicate which items aren't IDPA-legal, but be sure to read the relevant rule book before buying to be sure whatever it is you're interested in is legal for your game.
Holsters:
ReadyTac
CompTac (not available for a k-frame)
Master-Tac
BladeTech
CR Speed (definitely not IDPA legal)
Speedloaders:
Safariland CompIII
JetLoader
Speedloader holders:
ReadyTac
North Mountain (IDPA)
North Mountain (ICORE)
BladeTech
Safariland (not IDPA legal)
Moonclip holders:
North Mountain
North Mountain (IDPA)
ReadyTac
Johnson Precision
James Austin
Replacement Cylinder Latch:
SDM (OEM replacements; IDPA legal)
California Competition Works
Hogue
FO front sights:
HiViz
SDM
EGW
Also check out
Apex Tactical for their spurless forged hammer (only for guns with frame-mounted firing pins), as well as competition firing pins & springs.