As I mentioned above, brightness could well be a problem, but here are some pretty powerful LED's which might do the job for you, and are available in various colours:
**broken link removed**
As for MrDEB's suggested driver (with the FET), you could have the diodes series linked in three's, which would minimise the waste in the limiting resistors.
**broken link removed**
As for MrDEB's suggested driver (with the FET), you could have the diodes series linked in three's, which would minimise the waste in the limiting resistors.