Maybe a bit of penetrant oil or WD 40 and tap it a few times on the end with a small hammer to shock the threads.
These type extractors work very well, and maybe you can make a small one out of a nail if you have a grinder. Sharp corners are the key.
These type extractors work very well, and maybe you can make a small one out of a nail if you have a grinder. Sharp corners are the key.

Irwin 53635 5 Piece Straight Screw Extractor Assortment for Removing Screws and Bolts 3/16-Inch to 5/8-Inch and 5-Millimeter to 16-Millimeter,Silver - Threading Tap Extractors - Amazon.com
Irwin 53635 5 Piece Straight Screw Extractor Assortment for Removing Screws and Bolts 3/16-Inch to 5/8-Inch and 5-Millimeter to 16-Millimeter,Silver - Threading Tap Extractors - Amazon.com
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