[Kyd Campbell]

maybe this is what you’re looking for

https://www.sescom.com/product.asp?item=DSLR-5DMKII-HOCF

its specially made for Magic Lantern users and uses the AV jack, turning it into an audio jack, so no more video monitoring will come out of there, but it allows you to hear from both sides of your headphones. There are similar things for the USB port too.