Ring of quick change, which decreases the amount of time needed to put on and take off gear.

This could be a chargeable ring, which makes the decrease proportional to its enchantment (and a negatively charged ring making gear changes take more time). If implemented as non-chargeable, gear changes would most likely take a constant 1 or 0 turns.

One side effect of wearing this is that nymphs that charm you into taking off armor get fewer or no turns to make additional thefts while you are disrobing.