Rear handbrake mechanism for rear calipers

[Flyingfish]

Quick question as rebuilding rear my calipers soon as one is a little sticky.
Does anyone know if the cylindrical mechanism that fits inside the calipers are available to buy separately and from where?
BigRedd seem to do pistons seal etc… but can’t see anything else listed.Thinking of changing while they’re all apart to save future issues.
Thanks

 

[link]

I don't know if you can buy them separately but I'll warn you they're difficult to remove and even harder to put back in... I'd just remove the dust seal behind the hand brake lever and soak the shaft in some cleaner, then add a liberal dollap of grease!