Fun project, I wish you the best 
High intensity LED and a big reflector/lens is the most important part.
The bigger your optic is the less it will matter if you use a small size LED.
For anything below 30cm diameter I would recommend the SBT90.2, but if you go bigger then you can find larger LEDs that make more lumens for pretty cheap from china.
Feel free to use these calculators to get some rough estimates of your performance: Advanced calculators for theoretical lumens, lux, beam divergence, and more, of custom LED flashlights