Add to the above those DC-DC convertor modules, at around 1UKP (for a dual output, 5v -> +/-9v). Also some switchmodepower supply IC's can provide dual rail output with a small transformer, but thats probably overkill for your app.
If you just want the dual supply for opamps, dealing with AC (no DC offset) then you could just boost your 5v to something like 10v with a small switching capacitor regulator, and split that for a virtual ground. Not ideal, but for AC only signals, it'll work, you just need to remember to DC bias the output so its centred at 2.5V.
Sorry if I'm confusing you here, just sperting out idea's, the above posters have probably the easiest solution, and a 555 timer circuit does work, with shottky diodes it gives around -4V.
What sort of signal are you measuring with the PIC's ADC?
Blueteeth