http://www.halflife2.net/index.php?page=merch
That page lists the different versions, If you buy it over steam you have to download it.
So if you're on 56k retail is the only way to go, or get a friend to burn you the half-life 2 gcf files.
Those hydra files are material effects and add up to around 14kb, as far as i can see theres no model for it in the model steam cache...so its probably been cut. :(