http://www.Amayama.com
They are AUS based, but they get parts from either Japan or UAE.
Takes a couple days to fill the order, and let you know what is available.
From there, assuming they are available in one place or another, it will get shipped and arrive in good time.
Otherwise, you may have to try a European order solution.
Coltixim posted in a rather large info thread we started about brake systems recently, and he posted some good numbers with balance values.
You could try cleaning it out, and it would be cool to see if anything can be removed from the inside of the unit.
I haven't had one in my hands recently, so I can't say off the top of my head.
I suspect a unit with new springs would be best though.