Willie's post is a tad harsh.
I wouldn't worry over a magazine holder or white light/knife but its better in general to keep them concealed.
I prefer the covered style magazine/knife holders. It protects it better & is not obvious to the casual bystander.
New concealed carry garments & vests have started up since the late 1990s. 5.11 Woolrich SIG-Sauer Blackhawk etc can aid you in wearing firearms & carrying spare mags w/o problems.