Any particular brands you prefer? I have a Ping Rapture that's currently shafted, and somewhere is a Final in 12 -- it's a square Callaway clone -- some guy still has some new ones on the Bay: https://www.ebay.com/itm/Big-Final-9or10or12or14Beta-Titan-Driver-Golf-Component-Head-860-Illegal-Cor-460/163831693115?hash=item2625213f3b:g:LBAAAOSwMolZt0Cd
He's got a lot of other heads listed in 12 and a few in 14 -- I don't know whether he still actually has them, but the listings are there. A couple are 99 cents plus $9.95 shipping, a few $4.95 plus, and most are 9.95 plus. All clones, and he claims .860 COR, though I'd take that with a grain of salt