Well, what have you tried? You say you got it to work previously, what parts of your modifications are not working now?
I am ready to help, but I need to know where you are in the process, and what info you need. I believe we still have access to image.php in 4.5.X
So all you need is the productid! For instance:
http://trainingpen.com/image.php?id=16126&type=T