I think you actually might be able to get crafting materia simply from gear that has a majority of crafting stats on it, but I might be wrong. I have a crafting materia in storage but I didn't take a note of what I got it from. If you can get it from gear with crafting stats you can just battle in gear with those stats that are also DoW/DoM equippable.

That said I'm pretty sure you have a higher chance to get more "relevant" materia from converting tools/weapons. Both Dated Jade crooks I've converted have become Magic attack potency and Magic Crit potency.