The blades I linked to should be available in the states. The seller is located in the same state as me. It would be funny if he wouldn't sell to me.
The site you linked to has different looking blades, though.
Shredder blades would be ideal for the blackberries and grass. But it could be a while before I am able to collect the funds for a $800 Husky. That is a lot money for me.
I found a 21cc Echo SRM-210 at a local pawn shop. They want $90 for it but I should be able to buy it for $70. It might even be less than that. The Echo is a cable drive, not solid shaft unfortunately, but I can get a kit to convert the Echo to take blades. I am wondering if I could use one of the tripoint blades on the Echo for blackberries and grass. Or would that be to much for such a little engine? Not the ideal, I know, but I can afford the Echo. Then I could save for a Husky.
Could you swing $300? Try to find a used FS 250/130. Enough power, but not too tough on your wallet. And yes, I've cleared nasty crap with a 130 and shredder blade while the 450 was unavailable.