veganbikes

You cannot really have a geared fixed gear the whole idea of the fixed gear is it is one cog that is directly connected to the front chainring via chain (or belt potentially) that has no ability to freewheel and can only go in one direction. Potentially with some internal set ups you might be able to make gears work but generally most manufacturers either don't make a product or don't recommend their product for the task. Sturmey-Archer does make a 3 speed fixed gear hub (or at least did) but it didn't work well according to a lot of reports from people who have used it.

Your best bet is to use a dingle cog or chainring and manually shift or just flip the wheel.

Yes the madman inside of me really wants a Pinion to work because that would be awesome but I believe I did ask them at some point a few years ago and they said no but you could check again. However you would need a dedicated bike for that pinion is not just a bolt on system.

All this being said, the fun of a fixed gear or single speed is you are always in the wrong gear, not in a bad way really just you have to adapt to it.