You gotta have fretwire and there’s multiple flavors. We have it in different sizes, hardnesses and various alloys. We’ve even custom ordered special fretwire to our own crown and tang measurements for special needs. Our suppliers (Stewart-MacDonald, Jescar, Dunlop and Luthier’s Mercantile) can get us fret material in sizes from tiny mandolin wire all the way up to big fat Jumbo-style rails. Nickel-silver is the usual alloy for most frets but we stock and install stainless steel frets and can supply other, weirder stuff upon request. We keep the tubes of fretwire in a drawer but Fern recently moved the loose coils into the back stairwell where they can actually be somewhat categorized.
Reorganization in a small space is not for the faint of heart.