External GPU Very limited Use case

[Conker99]

I just got issued a new work mini PC. It's terrible. I just want to run at 21:9 ratio on my not even that great LG 34 that is about 3 years old. I also want to run one add'l screen. Intel i5 6600T HP elite desk. I am required to use this machine but I can ruin the case with a hole and I can add photo of my motherboard. I saw a video Linus did on "the beast" but the upshot of the video was, "this won't work." I don't want to do custom bios and I don't want to spend a ton of money. I have two old graphics cards at home I can use, I think GTX 960 or something like that, that aren't being used. With all that, can I stay under $100 and be pretty close to plug and play? Is there another option? Should I be able to download some drivers somewhere that will allow me to force a 21:9? Ok thank you so much.