Trainers.
You will have to look up a list of NPC's.
With this particular game the item will recharge over time by itself
On better char builds (non-magic based) I would have multiple enchanted weapons and rotate through them on an expedition. Get to a place to rest and sleep for some days and items will recharge.
If you're off exploring and need to recharge something then use a filled soul gem.
I would usually have a light dagger enchanted with soul trap and some unfilled smaller gems (although if exploring you usually find some) for farming and recharging.