I know Greg but this has been raised on the forums before.
And I said the same thing then as I am now, ignore the N/A, some S&Ps have it in the ISBN field, some don't.
While the magazine has something claiming to be an ISSN on the front this is not quite the same thing.
But to answer your original puurpose, I think, if S&P #9 is listed on the Online store (which it is) then it ios available to order from Mongoose if not elsewhere.
LBH