there are lots for sale.
they range anywhere from 2 mill to 6 mill to buy.
what you can do if you have a blacksmith and a imbuer is get a bunch of runic hammers, bronze and higher seem to work well, and make a bunch of boomerangs, then refodge them with the hammer.
set the re-fodgeing to do the 'of quality' setting and youll probably get one for about every 4 hammers or so.