Help please with bike after back injury

flyer

I had a nasty back injury last November and have been recieving treatment ever since, however my osteopath states that I should not ride a drop bar at the moment!

Please can you recommend a flat bar that is capable of doing an enjoyable 20-30 miles

I have been using a Roubiax Pro so used to a bit of comfort!

Just getting a few miles under my belt slowly, did 20 miles on my commuter bike Sirrus, but would like a bike with nicer group etc


Thanks

Flyer