Does anyone know where you can get a standard or uprated viscous coupling for the 4x4 gearbox?

I did find these, but I think they're quite expensive

Sierra 4x4:
FORD GEARBOX PARTS - FORD MT75 GEARBOX PARTS - FORD SIERRA COSWORTH & XR4x4 MT75 4X4 GEARBOX VISCOUS COUPLING (bearingkits.co.uk)

Escort 4x4
FORD GEARBOX PARTS - FORD MT75 GEARBOX PARTS - ESCORT COSWORTH MT75 4X4 GEARBOX VISCOUS COUPLING (bearingkits.co.uk)

BTW, I didn't know the viscous on the Escort is supposed to be stronger. Is this actually true?