Minimag aa upgrades?

I bought a new minimag aa just for the heck of it. It was $10 and came in an attractive deep blue color. The brightness is fine for me but it does have quite an ugly beam with holes and artifacts. Is that due to the bulb itself or the head design?

Are there bulbs available that produce a cleaner beam than the stock one? What are some fun ways to tinker with this light while keeping it an incan?