I can't be sure about the Shimano chains or 11 speed chains but have experience with buying KMC chains for 8, 9, and 10 speed recumbents where the chain length is more than twice as long as on a standard road bike. My local LBS wants an arm and a leg for three KMC X10.93 chains. I buy them online from a legitimate bike shop where they cut the chains from a bulk roll and sell it without the packaging. My last order was from Trailthis, a vendor on eBay. They have a sizable store in Mt. Horeb, WI and I can easily verify their presence here
https://trailthis.com/. I've recommended them to other recumbent trike riders and never had any negative feedback. My suggestion is to pick one of the sellers who has a real bike shop as they are unlikely to sell fake products that would jeopardize the store reputation.