The Beast uses the JST 'PH' connector.
My Beast pack building thread has links to everything you'll need to build your own lightweight Hyperion 2s packs from bare cells. The alternative is to buy the Hyperion 180 'UM' cells, and get the series Y-harness from Glenn @ RC-Connections. The links are also in my pack building thread.
Hyperion's 2s 180 packs lack the balance tap, but you could still use the stock JST 'PH' connector - you would just use the outer pins. The stock charger won't charge without the balance tap, so you'll either have to use an aftermarket charger or dissect the packs to add the balance tap. Glenn also has the JST 'PH' jacks & plugs - along with charge adapters for aftermarket balance chargers.
EDIT: Glenn now has a JST to Beast adapter that fits the Hyperion 2s packs that have the JST two-pin connector: http://www.rc-connectors.com/index.p...roducts_id=256
Hope that helps!