In D&D 3.5e, the wish spell can create any magical item. Pathfinder removed that ability from the “safe list” of wish effects, though, so ask your DM which version is in play in your game. Even with the Pathfinder version, it might still be possible as “greater effect,” but beware the dangers of using those—your DM will probably make you regret it, especially if they explicitly denied using the safe version from 3.5e. Even in 3.5e’s case, while the text of the spell explicitly uses the word “create” to describe what wish is doing, the subject of that verb is wish—not the caster. It is unclear if the caster has actually created the item, and is thus its “creator,” or if it is wish itself that is the item’s creator. Becoming the creator of a magic item (created by wish or not) might be a plausible thing to ask for as a “greater effect” in either system, but again, that’s extremely dangerous.
So far as I know, the 3.5e wish is the only spell capable of instantaneously creating a magical item. The true creation spell in 3.5e only handles non-magical items, and Pathfinder doesn’t even have that spell (despite its appearance on d20pfsrd.com—that would be the 3.5e version of the spell, copied from a 3.5e Paizo product, and not actually a Pathfinder spell). Instead, Pathfinder caps at major creation, which definitely doesn’t handle magic items. Searching d20pfsrd.com’s spell filters, nothing relevant turns up (I only searched on the sor/wiz list, but if it was going to be anywhere it’s almost certainly going to be there).
Beyond that, the only option I am aware of that might apply is Eberron Campaign Setting’s dedicated wright, which is a special homunculus that has the following ability:
Item Creation (Su): A dedicated wright can perform the daily tasks related to item creation on behalf of its master. The master must meet (or emulate) all the prerequisites to create the desired item normally, and pays the gold and XP cost himself. The only cost a dedicated wright can help with is time. The master spends 1 hour initiating the process, channeling spell prerequisites into the dedicated wright, and paying the XP cost to make the item. He may then leave, allowing the wright to carry the process through to completion.
(Eberron Campaign Setting pg. 285)
This description doesn’t clearly indicate who is the “creator” of the item, but since the master provides most of the resources and initiates the process, and further has a magic bond to the dedicated wright anyway, there’s a pretty good case to make for the master being the creator (or, at least, co-creator, which the circlet of spell-stealing doesn’t really handle).