1. Is there an extant magic item that grants the possessor the use of the Precise Shot feat for thrown weapons?
2. If not, how much would such a thing cost?
Well, generally I'm off the opinion that allowing characters to possess items that provide the benefit of a feat shouldn't be allowed. However, there is a bit of precedent for this sort of thing. I would look at the the Dark Blue Rhomboid which provides the feat Alertness. Arguably Precise Shot is much better than Alertness, but there is at least a precedent. It costs 10,000 gp.