I make 4 compartment ones with intumescent strips for 45 quid. Postage is around a tenner. They are fully compliant with HO guidance and accepted by all our local forces and I've sent a couple oop north with no complaints. If the rumours are correct that they will soon be needed for propellant as well I'm going to be busy!

https://www.dropbox.com/s/ntzb5iaz7v...02.47.jpg?dl=0

They don't have the interior lid now as Gwent police preferred the intumescent strip even though HO don't specify it.