I use these for just about everything..
Adafruit Pro Trinket - 5V 16MHz : ID 2000 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits - A -tiny- 5V Arduino. (I go through these like M&Ms.)
And then add this..
Adafruit LiIon/LiPoly Backpack Add-On for Pro Trinket/ItsyBitsy : ID 2124 : $4.95 : Adafruit Industries, Unique & fun DIY electronics and kits - A lithium battery charger that attaches to it.
And lastly..
Lithium Ion Polymer Battery - 3.7v 150mAh : ID 1317 : $5.95 : Adafruit Industries, Unique & fun DIY electronics and kits - Your 150 mah battery that plugs into it.
Done.
-jim lee