Any decent auto parts store (even the auto section of wal-mart) has a bulb selector. Just tell it what make/model you have, and which lamp you are referring to.
As far as making it brighter...I'd advise against a higher wattage bulb. I've read too many horror stories of melting the wiring and/or holders on these cars by trying to put a higher wattage bulb than was intended.
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