As
@Noob suggested, I would also lean towards Kydex one's as well. Quicker draw and safety options if you buy the one that fits with the specific model of your duty weapon.
Regarding comfort, I absolutely get that, it will also vary on his body shape and how and where he carries the weapon.
If he is allowed to get it, the I would recommend a Quick Locking System Kit, that he can mount on his belt so that he can carry and detach the holster as per his convenience and its more comfortable because the holster does not poke into the body anymore.
If he mounts it on his thighs then there are similar options for that as well.
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