Last I checked, Brickwerx sold good quality WPs. Cast impellers, nice machining. They also had the version with smaller diameter cog pulley (overdrive) for those that are concerned with overheating at low RPM/high load situations.
https://www.brickwerks.co.uk/t4-part...t4-aab-96.html
Why not change the WP at the TB change interval? Makes sense from a maintenance procedure efficiency viewpoint. Sometimes that's when the WP o-ring gasket is about to give up anyway. Otherwise it's a shame to have to open up and bend the TB cover to change out the WP by itself.