Zilla Custom Cabinets is a UK company which makes a range of standard size cabinets with a choice of speakers, tolex, grill cloth, piping, hardware and other construction options.  They also produce custom amplifier cabinets so if you're looking for something a bit different, oversized, light-weight, easy to carry, a combo extension cabinet or anything your heart desires they can make it for you.

Source: Zilla Custom Cabinets website (29 January 2020)