Spier and Mackay have a few full linen suits off the rack suits. They have bamberg lining, which is way more breathable than other off the rack suits that use polyester.
Suitsupply have made to measure full linen suits.
Full linen suits are hard to find because linen pants wrinkle really easily and therefore, not as popular. Linen is also a season, more casual fabric so they tend to be used just for jackets. If you're okay with just a linen jacket, like a sportcoat paired with wool trousers, you'll have a lot more options. You can get linen sportcoats at Spier and Mackay, The Bay, and even Moores.