Local parts stores like Autozone,Advance Auto & O'Reillys carries them,but they can sometimes be out of stock or on back order.You can find them on Ebay too,but everybody wants 2 arms & a leg for one,sometimes being priced at $300+.
Cardone is one of the major distributers for them,so try their direct site too.A9L (5 speed
& A9P (auto) are the ones to hunt,but other models will work too.The following link is a huge list of available ecms.
Fuel Injection Technical Library » EEC Program Codes