Spoke too soon :)
The literal name of the Export button is "ExportToExcelButton". In order to access the Export button, you have to do something similar to this (C#):
Button exampleName = (Button)e.Item.FindControl("ExportToExcelButton");
Took awhile to identify that the Export button had an ID of "ExportToExcelButton", as all attempts to access that (reviewing all properties, forcing a WriteLine of all of the IDs, ClientIDs, and UniqueIDs of the controls in the RadGrid, etc.) didn't reveal this information. Had to dig through several forum posts.