Mmontage is another one and Cleancutter.com is another option as well as Alamo. it might be simpler to go to a welding shop with the old deflector and have it replaced with a new one if you do not want to buy from Alamo.
You have to remember buying in quantity is the issue and anything under a hundred units will eat you alive uless you want mathews 3 inch grass knives(Y blades) at 1.11 each or so from my Mathews dealer and they do ship them.
They accept the 3/8 bore/pin/bolt etc., to hang them with the 1/2 by 3/8 oval punched in the grass knife; the distance from the top of the oval to the curve of the knife blade is 1/2 inch and the overseeding blades are even less in price per unit.
you will definetly have the advantage of purchase in bulk and having the leftover blades for the really crappy mowing areas if you have a lot of grape vines and brush.
buying two complete sets would give you a huge advantage in price if you do not have a hand held Mott kn ife grinder. I used my Wen wet well knife grinder and still have it to use.
I met the fellow who owns and operates Clean Cuttter at the Empire Farm Days last week, he is very nice and knows a lot about the business of flails and tillers too.