You can use a cordless drill in place of the Rotostart, it just needs to be able to have enough power to turn the engine over and turn it fast enough (the right gear ratio). I've used one before (a Craftsman brand) in a pinch, but they are bulky to use. You might want to check out eBay or post up a wanted to buy thread here in the right section, as I'm sure you'll find someone who doesn't need theirs or has an extra.
HTH...
Mark