I have GBs on another bike with 42mm hetres but there's not much room to spare. The hetres measure 42mm but the 44mm gravel kings measures about 46/47mm in real life.
I just saw that velo orange have some wider ones but I'm not sure they'll measure up to the GB quality.
Also Honjo but they are ££££
I've got a set of the 52mm VO Zeppelins, fitted recently and I really rate the quality next to GB ones. They do 58mm wavey ones as well, but they are twice the price of the GB ones you can find on eBay.
I have GBs on another bike with 42mm hetres but there's not much room to spare. The hetres measure 42mm but the 44mm gravel kings measures about 46/47mm in real life.
I just saw that velo orange have some wider ones but I'm not sure they'll measure up to the GB quality.
Also Honjo but they are ££££