Scooterotica

I have a few 5Ah batteries from work that I plan use to power spots with for occasional use.
My scooter is an AC model and so has no battery tray. There is a nice gap where I assume a battery tray is normally fitted. My battery slots into here nicely.

My question, has anyone any ideas of how to fix a battery in place in this slot without welding a battery tray in and preferably without drilling holes.
A long shot I know but some sort of strap arrangement is how I envisage it. I do use the filter housing by the way so there's an outlet and hose on the other side.

Thanks

Heres mine just some sheet aluminium bent to shape, with some foam tape, to cushion the battery and the strap is some thick rubber out of a "bungie" and a chain link for the catch/clip
It is bolted to the back of the toolbox , i did think about a lorry exhaust u clamp, clamped to the tube and the "tray" bolted to that. Which would be a better option for you if you dont wnt to drill the toolbox. I was concerned it may vibrate to much though.

Thanks for that.