I carry two spare mags in a snug synthetic open-top behind the point of the hip on my support side. That is where I carry for competition. That is where I carry for the street.
a couple good points brought up regarding not carrying the extra mag in the same holster. I can see if the need arises, it being more efficient to use my weak hand (left) to pull out and insert the new mag. Lots of good options here...I'm still weighing them, but am leaning toward a mag pouch.
I also think a mag pouch on the offside is the way to go .Check out kytex gear they make a great pouch for the shield.They are a small shop so making it and shipping takes about 2 weeks.But it is worth waiting for.My only connection to the company is they have made me some good gear.
The kytexgear.com carrier for owb with the shirt untucked or other cover garment. A nylon knife case with a belt loop for owb with shirt tucked or untucked. A remora or sticky accessory pouch for iwb. And finally, when I have an empty off-hand pocket I use the desantis mag packer.
Over the past several months with a single stack magazine, the Desantis mag packer or the nylon knife case seem to get used most often.