install el capitan on 2009 imac

I was given a 2009 imac without the password and managed to open it and make a new password and then install el capitan. Then I thought to factory reset because of other password issues and erased the drive. I really don't know what I am doing so didn't back it up. now I get a disk utility at start up asking to reinstall el capitan but when I go to the apple site, which seems to be my only option, After entering my id and getting verification code, they won;t let me download the os. It says error 403 forbidden. People have suggested that apple no longer does el capitan and that I need a bootable installer but I am not able to create it on my other computer. I have an oldermac which has elcapitan installed and it won't let me download the disk image. Is there a way to get that copy of el capitan on the newer computer? Any ideas? Does anyone have a bootable installer? I was hoping to go up to high sierra which it is supposed to take but elcapitan would be great.