Hey OP if you want to get back into cycling on a budget single speed that is really nice check out the Trek Soho, same price as the Kona but better for entry level riding.

The straight bars allow for a more upright position much like you will remember from your youth, but it still looks sleek and will feel fast with it's 27" wheels and thin tires. It's extremely light and nimble, and you can upgrade it easily later down the road depending on whether you decide to lean towards cruising or going faster.

There is a good looking upgraded Soho too with some innovative features, about $350-$400 more if you have it to spend.

If you want to recapture the feelings you remember from that first mobility as a child, get a bike like this rather than what all these kids are recommending. You will avoid back pain and have a better transition back into cycling.

Your initial impulse for a single speed is a good one to get what you want, ignore the kids telling you that "fixed gear" or "Track bike" is what you should get, it's utter bollocks and you will not experience what you remember. Those might be fun to try if you decide to get into more than one kind of cycling, but initially you've already got the right idea and I'd recommend you go with it. What they recommend simply isn't made for what you desire.

Good luck and ride safe!