I don’t recall where I bought my lock, but they are usually available on Ebay. For example:
http://www.ebay.com/itm/SCHLAGE-CUTAWAY-PRACTICE-LOCK-LOCKSMITH-TRAINING-PICK-ALL-BRASS-INTERNATIONAL-/221682532989?pt=LH_DefaultDomain_0&hash=item339d4f027d
There’s also nice selection here, but not with cutaway:
