Google "bike racks and top bags" and look at images. You can go as little at $20 rack and $10 bag (it's what I use on my mtb for winter trails) or as much as you want to spend. That will give you a "day ride" capacity. Also look at handlebar bags, but I prefer to keep the weight in the back.
__________________
FB4K - Every October we wrench on donated bikes. Every December, a few thousand kids get bikes for Christmas. For many, it is their first bike, ever. Every bike, new and used, was donated, built, cleaned and repaired. Check us out on FaceBook: FB4K.
Disclaimer: 99% of what I know about cycling I learned on BF. That would make, ummm, 1% experience. And a lot of posts.