Resolved Google Merchant and virtuemartXML export

I would like to change header for my XML export
Action:export
Component: Virtuemart
Operation: Google Merchant
I thought that it is possible for example throw override option (inserting file header.php with right content to specific path??) but this option is empty. Only - Do not use- option is here.
I need to use this header:

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:g="http://base.google.com/ns/1.0">
<channel>
<title>Profila Trade</title>
<link>https://www.profila.cz</link>
<description>Vše pro podlaháře a obkladače</description>

Not this wrong version which is in default option:
<rss version="2.0">
<channel>
<title/>
<link/>
<description/>

Can you give me an advice how can I do it?