Server guys bought a back up server without consulting me. Has a Rj45 Cat 6 10 GB port. Our Fexes are 1gb, which hook up to 9K's with only sfp slots. Will a 10GB sfp to RJ 45 connection in the 9k work?

So believe or not. Cisco doesn't make this part anymore according to this community thread.

https://community.cisco.com/t5/optical-networking/does-cisco-have-any-10g-copper-sfp/td-p/3807140

But there are aftermarket parts that seem to do the trick. I've never been one to do this considering you can just go twinax with a hba/fiber card, but do you think this aftermarket part will work

https://www.fs.com/products/66613.html?currency=USD&paid=google_shopping&gclid=Cj0KCQjwvIT5BRCqARIsAAwwD-RqZ0hKHHvTS4yAIIrobJZYT1LhehsITUSo_7bZ9M8BydKycUjX7JkaAj4kEALw_wcB