The issue that you run into with installing bulbs of higher intensity is heat dissipation. While you might be able to purchase bulbs of a higher wattage, you have to be careful about potentially melting the housings. As well, higher wattage puts additional load on the igniter and control unit, thereby limiting their lifespan, or potentially causing issues.
I'd simply search around online. There's really nothing I can recommend in this instance.
I'd simply search around online. There's really nothing I can recommend in this instance.