Wow, that thing must be ancient! I have a couple of the Tektite 3Cs from just after they started offering LED heads for them... maybe 4 or 5 years ago?
(grumble... grumble.... Google...) Bingo: Tektite 3C-8100-4
Hmmm... looking at their website, they're not offering that model any longer, so getting a replacement head to switch the incandescent out for LED is probably impossible. Never hurts to hit their CONTACT US page and ask, though! They might still have some of the old heads around.
http://www.tek-tite.com/contacts.php