I can suggest some options:
1. Post a thread in the "Wanted: Dead or Alive" section. One of your fellow forum members may have one that they are willing to sell to you. Try the other forums (TRF, RCF) also.
2. Buy an original from Ebay, one pops up every once in a while. Since this is a vintage, classic kit, it will probably command collector's prices.
3. Download the original plans and build a clone. Plans are here:
Standard components, like tubes, nose cones,etc. can be found at vendors like erockets. A complex rocket like this, however, might challenge your modeling skills, especially the non-standard parts which you cannot buy and will have to make. BTW erockets sells the laser cut fins for the kit here:
4. There is a vendor called Morerockets that sells kitted clones of classic model rockets. I have not purchased from this vendor, so cannot vouch one way or the other :