My "small rechargeable" setup involves a
Cygolite Hotshot and an
Axiom Spark 3, which appears to be a rebranded Serfas USL-3
The Hotshot I absolutely recommend; for the price its unbeatable, since its only a few dollars more than most non-rechargeable powered rear lights and is considerably brighter. Fantastic deal, my only complaint is that the hostspot is very narrow, so if its not aimed right its not very effective.
The Spark/USL-3 I use as a full-time flasher be-seen light, pretty much always in combination with a see-ing light (The venerable
LD20). Its only bright enough to see with in very, very, dim conditions and at relatively low speeds. It has an integrated stretch-mount. I find this convenient because I can put it on my bike, my helmet, or my friends' bikes with equal ease, and of the three strap lights I've had none have ever failed/come undone.
I've known several people with the the Flea front light, and from what I've seen its considerably brighter than the Spark, but the downside is lower battery life. Also, they have a specialized little piece that allows them to charge, and one of the things that has held me back from ever getting one is the fear of losing a small, nonstandard piece. Both the Spark and Hotshot use a standard mini-USB cable, the kind that connects to an external hard drive, an E-Book reader, and some cell phones.
Any thoughts on just investing in some
good rechargeable AA or AAA's? They're not as energy-dense as the lithium-polymer nonchargeables in the above-discussed bike lights, but you can use them in any lights you have. They'd be the cheaper solution if you already have a lightset that fits your needs.