Battery no charging, stator problems?

[pinchepunx]

So after taking my bike out on a cold Chicago day I drove 20 miles to work, then 5 hours later I drove 20 miles back and my bike died as I was pulling in the driveway. Thankful and lucky it got me home. This is a new battery and I am assuming it is just not charging while riding (I keep it on a trickle charger at home when it's not in use).

Am I correct in assuming the problem is the stator?
If I replace the stator, what is a good aftermarket brand? Or should I go OEM? (more expensive?)

Thanks!!!

JM