Just to add to the mix here.
I collected my pre owned Grenadier last week. It came with a slip over wheel cover (something that Grenadier suppliers are putting on, as it has their logo printed on).
I popped into my local Grenadier supplier to register my vehicle with them, and asked to order the lockable box.
Once he’d ticked all the boxes for each individual part (it’s not supplied as a single item, cheeky buggers) which consisted of many, including three foam inserts at £12 each (+VAT), the tally reached over £500!!!
Order cancelled with immediate effect.
Moral of the story: order it through the configurator.
Even the blank insert is around £120, but as a previous member said, you can at least use the wheel to store some non value items in there, such as snatch straps or similar.
But make sure whatever you store is sealed in bags, as the rim will allow water ingress from the back.