There are few antibody that can be used for human brain samples. For details you can see FoxP2 Antibody (NB100-55411) - Novus Biologicals and FOXP2 Antibody (MA5-31735) - Thermo Fisher Scientific
https://www.thermofisher.com › Antibodies › FOXP2
Invitrogen Anti-FOXP2 Monoclonal (2G11B8), Catalog # MA5-31735. ... This antibody reacts with Human samples. ... Species Reactivity. Human. Host/Isotype.
Anti-FoxP2 Antibody is a Rabbit Polyclonal Antibody for detection of ... FoxP2 in 10 µg of L6, NIH/3T3, mouse brain, rat brain, and human brain lysates
Hope you will find the possible source of antibody that is reactive for human brain tissue.
Article Foxp2 Mediates Sex Differences in Ultrasonic Vocalization by...
This continues to be such an interesting gene to study. My favorite basic science paper cites the Abcam antibody. This product lists it detects human FOXP2 protein: https://www.abcam.com/foxp2-antibody-ab16046.html