I have one alternative not mentioned so far.
It doesn't have spot metering but with its ESP matrix metering you might not need that.
The OM-PC (OM-40).
It is ~functionally~ the same as the OM-2S but the manual spot metering is replaced with ESP metering, which does wonderful things for slide films.
So it depends on how you intend to use the spot meter. If it's to average out the scene or take into account backlit situations, you might consider an OM-PC.
But, like the OM-2Sp, OM-PC seem to have a higher failure rate and for both models there are a lot of 'parts' cameras out there. They are practically unrepairable so be careful.