Originally Posted by cubewheels

Adjust your saddle and try moving it forwards if you haven't already, this is the simplest solution to move into more upright position (albeit, only a little bit more upright).

One thing that can bring you to more upright position (by a large degree) is the beach cruiser handlebar.

A higher stem that is rotated backwards (facing you) is another solution (but let's hear about the experts here concerning safety) that can make more upright by a large degree. However, this solution can look weird and may attract attention from other cyclists.

A non mechanical but very simple solution is to strengthen your core muscles (use your core muscles instead to support your upper body weight instead of using your hands)

And finally, neck and back pain is very likely caused by wrong bike fit (for example, your saddle might be tilted nose down too much). If you can afford professional bike fitting, then go for it....BUT, if you like to do your bike fitting yourself, you can also do it browsing through youtube videos concerning bike fit like this example:

https://www.youtube.com/channel/UCr4...L1xJb4A/videos