Is this for use with an RO unit or am I missing the point?
If its for an RO you can just buy a vessel and add the softener.
I not 100% sure but I thinhk you can recharge the softener with standard dishwaher salt.
If its just the softener and not for use with the RO THE B&Q sell metered water softeners for upto 6 people to a house hold. Around £500
Dave