You could check out Mountain Electronics. Richard, the owner, is a member here. His nick is RMM. He has designed a buck driver called Mountain MAX. His site claims to be out of stock on those, but he might build you one if you ask him. They are capable of ~16.8V input.
Can anyone help verify that it’d work with a 12V LED? It doesn’t actually specify and KaiDomain didn’t respond to an email (sent last week). I’m guessing its for 6V because of the 4.5-5A statement but MTN MAX says the same for theirs but the output current can be adjusted.