You don’t have to generate thousands of files… have the files generate on the fly when they Click the button.
You save a copy of the “sample” xml file which looks like this and you store it on the server
But replace the RecordID with a easily unique “template” flag for example {REPLACE_ME_AT_RUNTIME}
Then when the user clicks “Launch In Epicor” you simply read the XML File in do a replace of your {REPLACE_ME_AT_RUNTIME} with the PartNum that you want and output that file down to the browser which will prompt you to “Save” or “Run” if the user clicks “Run” it will launch Epicor proper.