I hear Magnoli or Fenix Props are good for gloves, I got my shin guards from Portumac and they are great looking. Definitely contact KevVader for accurate chest box straps, as well as AceReplicas for the belt boxes, his are machined and are great looking.
As for the mannequin, I ended up grabbing a 6'4'' one off ebay and modified it by bulking it up using bubble wrap and tape, as well as heel risers and insoles in the boots to bring it up to a height of 6'8'' in full armor.
However, if you're looking for a perfect size mannequin straight off the bat, mannequinmode.com features a 6'5'' tall muscular male mannequin. Jump over there and take a look, I believe they run for around $200+ though.
Absolutely check out the 501st sith lord detachment forum. Nearly all the Vendors I mentioned are active there and will take orders through a 'general store' thread.
Good Luck with your project.
-Vince