A couple things. You're kind of putting the cart in front of the horse. Before even thinking about buying armor, please take the advice that you need to square away the foundation garments first. The finest armor will not function properly without well fitted arming garments underneath it all, and that armor needs to be sized to the person with those garments on. This is especially true with plate armor.
Secondly, let's try to narrow down exactly what you're looking for. Here are some representative harnesses from different time periods ranging from the late 13th century through the 14th century. Any of these float your boat? If one jumps out at you we can really narrow down what it is you should be looking for both for hard and soft kit.
Later 13th Century Templar Kit, could easily be a secular crusader instead of monastic order, predominantly maille, with steel knee cops, Bolzano style great helm
Later 13th / Early 14th Century secular Knight kit, still predominantly maille, with more plate features, Coat of Plates, Sugarloaf style great helm (or Bolzano still in use), more developed knee protection
Mid 14th Century knight, coat of plates, open faced bascinet, plate arm defenses worn beneath a short sleeved maille haubergeon, plate knees and padded cuisses (could easily do splinted cuisses as well for the thighs and splinted greaves). Could also sub in a klappvisor flat-visored bascinet, or early klappvisor with pointed visor. Wisby style gauntlets.
Also a mid-14th kit here, just
ignore that side hinged flat visored bascinet that's not really something I've ever heard of being documented. A little more developed than the other mid 14th. Note the Pembridge Style Great Helm that can be worn over that bascinet or cervelliere.
The archetypal Late 14th century kit, houndskull bascinet, fully developed plate harness, coat of plates or full plate cuirass, hourglass gauntlets
And to cap it off
here's an early 15th century kit, Agincourt era and a little thereafter. Fully developed plate, a Great Bascinet (rigid neck defense, rounded visor)
