iTunes Purchased By Tag

Hello I Want To Change Purchased By In Songs Of iTunes
Please Help Me :unsure:

No Support for this field in Mp3tag (yet) only support for Itunes Account (so email address)

An Unsupported way could be (Not tested):

Edit the Music File (1 by 1) with a Hex Editor, but very (x4) careful for corruption.

This explains a Hex Editor: http://en.wikipedia.org/wiki/Hex_editor

Another Option (also not tested, so not sure)

Convert the m4a to Mp3, good chance is, that specific tag will not survive the conversion