These mouse pointers are kind of a strange font file.
 
 And they live in the X11 fonts folder filed under 'misc'
 
 Just make a backup of the original to say cursor.pcf.gz.orig
 then copy over the one you want, renaming it to cursor.pcf.gz
 
 Restart X and you should see your new pointer.
 

 So far these are the cursors I have;
 
 qnx.cursor.pcf.gz - black with white outliine (QNX Photon)
 white.cursor.pcf.gz - white with black outline (downloaded)
 xorg.cursor.pcf.gz - black pointer from xorg dist on OpenBSD