https://www.amazon.com/10GBASE-T-Transceiver-Compatible-Ubiquiti-SFP-10G-T-UBQ/dp/B07BHDJKRD?ref_=ast_sto_dp&th=1&psc=1

$44 per from Amazon; work well... I don't think you are going to find used ones for a whole lot cheaper. They are inherently expensive :\

Pay more $$$ to go longer distances.

But be aware that longer distances means more wattage.

30m is roughly what you should expect.

https://smile.amazon.com/gp/product/B07BHDJKRD?th=1

https://www.fs.com/products/89572.html

https://smile.amazon.com/dp/B06XQBFHNL/

I have this one and it works just fine. I've never speed tested it, but it worked as a temp connection when transferring data from NAS to NAS.

AMAZON LINK