The problem is $$$ (and tightwads at the top)
The only bought the rights to the art, for the print version covers.
@ GMW if you don't have it. Get the (calibre) Search the Internet Plugin
Searching Google Images comes up with better (the ones that match my 60's issues, covers) selection.
Click the 'found' results (really a thumbnail), to open the real image: Drag that onto the Details (or info, or cover in the MDE) to get the listed size