I've also got Camelbak type (see foot note) Hydration packs (no bladders, yet) for $4.75. It's more cost effective to be shipped with a larger order because shipping is about $7 for the hydration packs alone. FootNote: The hydration packs are USGI surplus. They are various manufacturers (No choice in mfg), although about half are Camelbak brand. Regardless of manufacturer, they are ALL identical inside and out.
okay then. I've got the bladders in (3-liter) for $14.97 each (new). They're on the site. Coupled with one of the Hydration Packs, you could have a fully functional hydration pack for a hair under $20!