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I am not aware of any magazine that will readily interchange.
I suggest that you take the firearm and keep it. Then do a little research on getting another.
When researching a new firearm, look at what is available. The Glock and the 1911 have tons of aftermarket magazines (and mag carriers). There are plenty of holsters around., too.
Some of us have purchased firearms in the past without thinking of aftermarket stuff, and have been "stuck" with a firearm that has one mag, no holster, difficult to get fixed if something breaks, and sits in the safe most of the time. Learn from our "mistakes".
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC