I'm not sure where you could get a 12V MCPCB but you can buy the 6V 5050 (XHP50.2) MCPCB in 26mm on Sofirn's AliExpress shop. This board is part of the Sofirn SP33. As it is an individual request you need to send a message to the seller asking for this board. They will eventually answer and tell you the price (approx. $ 2,00 per MCPCB).