No aftermarket products for it. You really shouldn't need anything....it's already VietNam era.
If you are looking for instrument panel gauges, seatbelt harnesses, etc, try the 1/24 scale car aftermarket section of your local hobby shop. Some aftermarket items for 1/24 scale aircraft kits may also be useful.
Also search this forum for '1/24 Huey'. There are some very good discussions of this kit.
Joe.... who has five different boxings, starting with two, yes two, Phantom Hueys.