Have to say I’ve never seen one for sale mate - it seems most of the people on here make their own from scratch - or customise other old boxsets they no longer use, or have gone out a bought an older cheap one.
Maybe some of the dvd cover forums will have a better idea - or a link to where the film distributors buy theirs from (though could be looking at a significant amount of minimum orders etc?)
Good luck with though mate - be great to find a good value-for-money place that does 😃
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May be worth asking in the comments section on these type of ‘make your own dvd box set’ videos too? Hopefully you’ll get an answer or a link etc:-
https://www.youtube.com/watch?v=j3QvlNLE0Iw
https://www.youtube.com/watch?v=KF1ikJEvOfc