I've bought a lot of Lee Filters from BH Photo. As already noted they are frequently out of stock, you have to be prepared to buy them as soon as they're in.
Case in point - two weeks ago I bought a .9 Soft Edge ND filter. They arrived in stock, I bought the next day, the day after that they were out of stock again.
Last week the 82mm wide angle adapter ring was in stock... I bought it the next day, the day after that it was out of stock again.
So be prepared to jump on it as soon as you see it otherwise there is a good chance you'll miss out.