There is no way to override the program file header in PxBasic, however more importantly you should not
be using PxBasic to develop/maintain commercial applications. It is intended for personal or educational use.
The following is an excerpt from the PxBasic license:
You may only install and use your licensed copy of PxBasic in a manner that is not primarily or otherwise intended for or directed toward commercial advantage or private monetary compensation whether direct or indirect.
The full license can be found here
PxPlus does allow the override of the program header and in fact uses the legacy [Pvxprg] header to preserve compatibility with older products.