battery bracket nut broken when replacing battery

[physhy]

Hello I replaced the battery on my 08 M3 GT today. When I opened the cover I discovered that the metal bracket holder nuts were extremely rusted on both sides. I applied some penetrating lubricant. I was able to remove one of the nuts successfully but the second one broke off. Is it possible to replace that metal screw that the nut holds on to or do I have to replace the whole battery box/tray? (Please refer to the image). https://ibb.co/X8X3L54

Should I leave it just held by one side? other recommendations?

When removing the negative terminal the nut that holds terminal tight to the battery post also broke off. Luckily the part that its still there is holding the bracket tight but I want to replace it. What part number is that screw/nut?

Thank you for any help/suggestions

[G ~ MINI]

No image !

But if the bolt and nut can be removed entirely why not replace with a something that fits from Home depot.
Or replace both with new stainless steel

[physhy]

not sure why it didn't upload here goes again

https://ibb.co/X8X3L54

[physhy]

not sure why the upload site that I'm using doesn't workhttp://gtitc.com/files/s-l1600-m3.png

[physhy]

this is the other nut/bolt that broke https://gtitc.com/files/s-l1600-m3-2.png