Can you post a photo of your engine ? I don't know much about them, but I do have one. If you post photo, maybe sommeone will recogonize it and respond with your requested info.
I use an NGK CR5HSB in my Honda GXH50 and i think they use the same plug. You might have some luck finding it at a NAPA or Carquest- an old school auto parts store with a grimy counter across the back (the best kind), but I could not find it at Auto Zone or Advance. I ended up getting mine at a small engine and equipment dealer.