The Helium Carbon ($495 CAD, 950 grams +/-) has a lot smaller overall shell size and is substantially lighter than the Blade Carbon ($475 CAD, 1250 grams +/-). Part of the weight savings on the Helium model are due to the large venting and cut away EPS throughout. The Helium helmet is ECE rated, not DOT and ECE like the Blade.
I ended up buying a new model 509 carbon from Recreation Supply here in Saskatoon. Price was better than the Canadian and US mail order places.
Kijiji had a newish 509 carbon, last year's model, in Medicine Hat yesterday. Decent price and I liked last year's color selection more, but wasn't saving enough to justify a used helmet.
Check out B-PWR from Quebec. Claude is the owner used to work for BRP years ago. Makes a sweet helmet. His non carbon helmet weighs 1260 grams! Super light and sweet looking. Also is ratchet strap type