Links (some no longer available, but give you an idea)

Shotgun shell arm belt: GVN 8 Rounds Gun Ammo Storage... https://www.amazon.com/dp/B072QCYZTQ?ref=ppx_pop_mob_ap_share

Shotgun shell body belt: 1 X AIM Sports 56 Round Shotgun... https://www.amazon.com/dp/B0062CAGXQ?ref=ppx_pop_mob_ap_share

Drop leg pouch: Military Tactical Drop Leg Bag... https://www.amazon.com/dp/B072N84B85?ref=ppx_pop_mob_ap_share

Tac pouch (for 7rd mags): Protector Plus Military Tactical... https://www.amazon.com/dp/B0171NQUT8?ref=ppx_pop_mob_ap_share

Shoulder holster: UTG LE Grade Vertical Shoulder... https://www.amazon.com/dp/B002TUSSNU?ref=ppx_pop_mob_ap_share

Harness (for when I don’t wear a shoulder holster): Men Paddded Adjustable Tool Belt Suspender Duty Belt Suspender Tactical Duty Belt Harness For Duty Belt https://www.amazon.com/dp/B071J61ZK1/ref=cm_sw_r_cp_apip_7mi4V9bOAq4Kj

Drop leg holster (I got a slightly different one that is reversible, since the harness is defaulted to right handed): Drop Leg Holster, Right Handed Tactical Thigh Pistol Gun Holster Leg Harness https://www.amazon.com/dp/B071RNS9MX/ref=cm_sw_r_cp_api_glt_fabc_NW57M64D1G2YGYKHTC2N

Hope this helps!

Edit: shotgun shell items are for holding canisters and 10rd tubes

Edit2: all the items here that have mag holders - the dropleg and shoulder holsters - fit 7 round tubes (but tight, so they do expose slightly). I haven’t found anything else that’s worth getting for quickdrawing mags, but reloading takes so long anyways it barely even matters so I keep them in a pouch. The drop leg pouch is for bigger mags like the zetas.