The problem in general is the AMD graphic card, you can find the chip itself on ebay. But you have to replace it also with your damged chip. So you have to look for a company who does that. Try google 'macbook pro 2011 video card replacment shop' or if your up to it try a liitle coding as an altenative fix. [guide|115126] or if that does not work try https://forums.macrumors.com/threads/force-2011-macbook-pro-8-2-with-failed-amd-gpu-to-always-use-intel-integrated-gpu-efi-variable-fix.2037591/
Depending on the situation of your Macbook pro it can be real easy or kinda complex.
hope this helps