Kromlech has released their Stygian Legs, which obviously are perfect for your Thousand Sons.
You can find these on the Kromlech web store on eBay.
These go with their Stygian Shoulder Pads previously released:
Scibor has released another amazing 28mm figure called Cezar of Rome.
It goes with their entire Roman Legionnaire army figures, which are a great proxy for Adeptus Custodes.
Max Mini has new Officer Heads.
And Puppets War has previewed their new Destroyers.
So go forth and customize!