Put it on your wish list.

Phrase derived from a common online shopping option, but now used in colloquial speech to indicate that a requested action or item is beyond the pale and will not be honored. Often accompanied by a W hand-sign formed by an angled linking of two L's using the thumb and pointer finger.

You want to borrow my first edition copy of Alfred Bester's The Demolished Man? Yo, put it on your wish list.