Some recently released defenders from English Championship level. Plenty of experience, not too old either.
https://en.wikipedia.org/wiki/Shane_Cansdell-Sherr...
https://en.wikipedia.org/wiki/Karleigh_Osborne
https://en.wikipedia.org/wiki/Ben_Turner_(football...
https://en.wikipedia.org/wiki/Scott_Wootton
https://en.wikipedia.org/wiki/Kelvin_Wilson
https://en.wikipedia.org/wiki/Lewis_Buxton
https://en.wikipedia.org/wiki/Lloyd_Doyley
Also Neil Kilkenny