Generating plus and minus voltages for op amp
The cheapest solutions, assuming you only have one supply, are to redesign the circuit so it will work from a single supply or generate the negative supply. All monolithic op-amps that I know of will actually work on a single supply- very few actually have a ground pin, so they don't know the difference between +/-5V and a single 10V supply. They do know (and don't like) signals going below the negative (or positive) supply, or even approaching it in many cases. I suggest you look at the datasheet for the LM324 which is a so-called single-supply op-amp, so-called because the output swings close to the negative supply (with a load to the negative supply) and the input common mode range includes the negative supply. There are many examples of circuits operating from single supplies in the full datasheet. A rail splitter 'chip' is used in none of them, but occasionally an extra resistor or two is required. 

For example, as you mention a multivibrator: 



The LM324 at a penny or two per op-amp may not be as fancy as your expensive 10-cent op-amps, but it's ubiquitous. Many of the circuits are limited by the (frankly, not spectacular) performance of that particular op-amp but you can subsitute something better if you like. 

That just isn't very elegant in some cases- especially when things are DC coupled. In such cases, you can produce a negative supply with a cheap switching regulator or a charge pump chip such as a 7660. If you have a clock available, a charge pump can be made with a digital output, two MLCC caps and a dual diode.


  “An engineer can do for a dollar what any fool can do for two.”
  
  ― Arthur Mellen Wellington