I did look into it when I bought my big beasty, I've just never been able to get anything off the ground!!!
TBH if I could get XF pink things I would - just to p*ss off my friend, she is the Trinny & Suzannah of the equine world. God Forbid your horse should wear something that doesn't match it's colour!!!
If you ever find a solution- please let me know. Trying to find anything for my 18hh+ is a nightmare. Although I hadn't thought of the option to change horse......!
For my big boy I have my bridles made by a local woman. He is still in a 7ft 3" rug (for the time being) which are easy to pick up at tack shops. Saddle was another thing though
Barnsby do their bridles in extra full aswell if that's any good.
Also recently found that Aerborn do grazing muzzles in extra full that are similar to the shires ones. It's a pain in the bum trying to find extra full stuff!