Brownells sells the taps for $2.49. Part number is 395-648-001 for the taper tap. The plug and bottom taps are the same price, and you can look up the numbers for those.
You won't find a better price for a decent tap. The taps are made by Hanson.
NRA Endowment Member Bolt&Barrel Gunsmithing, Greenwood, SC www.boltandbarrel.com U. S. Army Veteran