As far as i know, the S25FL116K series from Cypress may also work (i vaguely remember reading about someone using a S25FL116K NOR flash in his OSSC 1.5 build). It has the same memory size, the same pinout and it works with the same voltage range (while drawing almost the same current). Size-wise it should fit too – as long as you buy one in the SOIC-8 package… like the S25FL116K0XMFB013. The only difference: the S25FL116K series is suitable for higher clock speeds… but it should work with lower ones too.
There are some substitutes from other manufacturers (like the SST25VF016B series from Microchip Technology) with very similar specs – but i’m far too less experienced in electronics to give a definitive answer about their usability.
Last but not least…
You can still buy some old-stock-leftovers ( <- i guess) of the S25FL216K series on AliExpress:
But apart from that those flash chips seem to have vanished from the catalogs of every big electronics distributor, since they are not manufactured any longer and the remaining stock of the manufacturer is likely used up.