where to buy L-pad 50w 16ohm

[adamskiuk]

This might seem like a rather silly question but does anyone know where to buy a L-pad 50watt Attenuator pot in the 16ohm version to use as a master volume mod for a smaller amp. I can see loads of places selling the 8ohm version online but none seem to stock the 16ohm required for most guitar amps?

Any help appreciated

Thanks

Adam