How to avoid ±voltage on capacitors in astable multivibrator
Have you considered bipolar electrolytics? Normal electrolytics only have one plate doped (if that's the right word), so they can only withstand a unipolar signal (in reverse they act as a short, if I recall correctly, which is what causes them to bulge and eventually vent/explode.) Bipolar electrolytics usually internally have two capacitors connected in inverse series, or, in some cases, both plates equally doped. You can create the same effect in a pinch by wiring two electrolytics in inverse series, like this. 

  |  / +  + \  |
--| |--------| |--
  |  \      /  |


You can also get axial ceramics in values up to around 1µF, and bigger in surface mount sizes (I use 22µF 6.3V 0805 capacitors.) For example here is a 1µF cap rated for 50V.