Are you looking for the convertible or XJ-SC storage compartment ? I have the compartment from a convertible. I bought it for my 88 XJ-S coupe but have decided to go in another direction for the rear seat delete.
The convertible has a single locker box lid, while the cabriolet had two separate compartments/lids. I’ve found the cabriolet approach actually better in practice than the large single lid the convertible has.
On eBay at the moment there is a cabriolet locker box for sale – 323623429920 – which could possibly be fitted to your convertible (I’ve not got both the convertible and cabriolet stored near each other so can’t actually check this myself).