We have an Equipment listing which covers a large assortment of items. Some items are on there for reference. For example, you can find chains, which describe how much strength you would need to be able to break them. You can find drugs, which describe the mechanical effects and local prices. Just because it's on the equipment list doesn't mean you have to exhaustively itemize everything you own.
You MUST purchase any item that you wish to get mechanical benefits from (weapons and armor are thus explicitly required to be purchased). You also MUST purchase any item that is trackable (vehicles and phones are explicitly trackable) if you want to say your character has this item.
If it's just a miscellaneous but potentially useful item you could pick up at a store (bolt cutters, lockpicks, duct tape, etc.), you can simply say that you have these things so long as you do it at the beginning of a scene. You cannot just so happen to have XYZ on you the second the need arises mid-scene, even if it makes sense for your character. Either you have it in your +inv or you declared it ahead of time, or you didn't.