I made my own with 2 x lengths of 10mm threaded rod, 6 x nuts and washers to suit, and a piece of aluminium extrusion with a random bit of rubber under it, cut and drilled to suit ..
If you lift the washer reservoir out of the way you can access all you need to undo the battery tray from its mounts on the firewall and engine bay. You will find that there are holes already in the bottom conveniently (for me) in the right place and just right for the 10mm rod. Clearly you need to assemble the rods in place before you bolt it back onto the car .. then simply slip the battery between them and bolt on the top part.
Coupla pics of it finished : Sorry : too dumb to link them directly !!
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