Why exactly do you want the 125B? From what I understand it is being replaed by the Quark SSB-mk3.
This. The SSB looks nicer and hopefully has the heat issues that the 125B had solved.
And... the MMM is just weeks away or less.
If you really want the 125B Ebay may be your only option. It seems that Quark isnt shipping the 125B any more.