Purchase is a perfectly good use to mean 'grip' in my opinion. OneLook defines it (inter alia) as "the mechanical advantage gained by being in a position to use a lever". I wouldn't say it's especially colloquial.
Build a man a fire and he's warm for a day. Set a man on fire and he's warm for the rest of his life.
Seems to me that this thread has quickly come full circle: SHU: prize/pry/grip R.E.: prise Asa: purchase/grip Arnie: purchase/grip/lever D.H. (me): lever = pry as in "pry bar" or even as in the local colloquial "bait and pry" meaning "Fulcrum and lever".
price < ME pris 'value, price, reward' < OF < L pretium
prize 'something offered or won' < ME pris
prize 'something seized by force as booty' < ME prise 'taking of something' < OF prendre < L prehendo 'to seize'
prize 'to move by force; leverage' < ME prise 'instrument for prying' ? < ME prise 'taking of something'
pry 'to look closely' < ME prien 'to peer in' < ?
pry 'to raise or move with a lever', variant of prize 'to move by force'
purchase 'to buy' (also the grip to prevent slippage sense or a tackle or lever; < ME purchasen 'to pursue, purchase' < OF purchaser (< pur- 'forth' + chacier 'to chase' < VL *captio 'to catch').