There's a line of "templar knight" type outfits in different colors, unless your asking for full armour type suits if so theres 1 or 2 of those I believe. Check AZ4 item search & use the keyword "knight" or "armour" & it should show you all the available options. Untill PSN installs a store search feature of their own this is the best way to find any Home item.
Here's some knight outfits and where you may find them.
Death Knight (Konami>Male>Halloween)
Age of swords knight outfit bundle (VEEMEE>Age of swords>Male>Value packs)
You can also find four knight outfits under Heavy Water>Avalon Keep>Male>Value Packs
Here's the link for them - http://alphazone4.com/store/cat/19644/
I hope this all helps.
Too many to post. Follow this link & all the items are there.