Rainsoft Gold replacing bypass valve

I've looked through the forum and online and it seems that the Fleck 5000 is recommended as a replacement for the Rainsoft Gold but I cannot find that model (only the 5600 which states it's for Rainsoft Silver).

The unit was bought in 2004/2005 and Rainsoft "serviced" it about 9 months ago. Basically, I'm seeing water leaking from the spacers. Do I just need to replace the spacers and seals? Really, it would be great if we could replace the bypass valve (assuming that would include spacers/seals) with stainless steel.

Does anyone know if there is an alternative to the Fleck 5000 that is compatible with the Gold series? Any tips on replacing? Are any of these parts available at hardware stores (e.g. Ace) or do you have to get them through a dealer/online?

Thanks in advance for your help!!!