This is a funny comment because just last week I bought a second-hand copy in Berwick-upon-Tweed. I haven't read it yet but it's been on my list forever and it's a mint copy with a nice yellow cover. It was published in the UK as part of the "SF Masterworks" series which is a trove of previously out of print stuff. If you come to London again you should find it in most large bookshops like Waterstones.

Did you try asking shop staff? You might have happened to be in when the shelf was dry but the stockroom had a copy. This isn't really an oddity.

It's everywhere in any major bookshop in London like Waterstones and Foyles

And once the TV series is out, you'll see it even more

For what its worth, I just checked my local Barnes and Nobles in the suburbs of New York and they had it.

You could check it out from a library and just not bring it back. They'll charge you the MSRP.

Check large chains like Indigo Books in Vancouver - Gibson lives there.