No Cost Items (Samples) on PO's

Hi,

Occassionally we have no cost items (samples) that we want to put on a PO for tracking and place in a work order.  What is the best way to handle these items? The problem that we encounter is that because they have no cost we can't receive them.  The items are defined in the item master as Type P, line type S for stock.  I don't want to put a cost of .01 because that will create a liability to write off in A/P.  Should these be defined as non stock items until we make a determination that they will be stock?