I use Island 4x4 as their site states plastic or metal
here is metal
https://www.island-4x4.co.uk/water-pump-stc2192g-stc3342g-metal-impeller-p-1389.html
and here is the plastic
https://www.island-4x4.co.uk/water-pump-britpart-stc2192-stc3342-plastic-impeller-p-18167.html