Sorry about the opa192 - I'll look for something else. And the 7660 is no good - it's a psu chip- my mistake - I meant the 7650 - but that's no good either as it's input only goes to -1.5 volts from the +ve rail...
Not many opamps will do for this, unless you're willing to use a little (isolated) 9v battery and replace it every 100 hours or so - that would make things much easier.
Would that be OK?
Allan