You can get a rechargeable battery pack with brackets to mount the starter in - with a charger.  Don't know brand names or details but I know some use them.  Others have home-made 'cases' that have the starter/battery mounted in a similar manner.

I use a 'pit box' that has a 12v. battery and a power panel and just connect starter leads to the 12 volt output of the power panel.  The box has a 12 volt gel-cel or lead/acid battery that I recharge occasionally with a small 12 volt automobile charger.

In actual fact, I seldom get the starter out of my big tool box - I really don't have much trouble starting most of my engines by hand.  If I have to flip more than 3 or 4 times, though, I usually start thinking about the starter.

<edited to add>:

Here are a couple of options --

http://www3.towerhobbies.com/cgi-bin/wti0093p?&C=PCF