Problem is that the stepper driver is expecting to see 5 volts, any recommendations for a level shifter that will work fast enough for this?
In case you are using those small drivers like a DRV8825 or a A4988 -> they are directly compatible to 3.3V outputs so no need to level-shift. In case you use one of those larger optocoupled drivers like a Leadshine DM556 or similar you can try if it works directly with 3.3V (it usually does for me) but this is somehow borderline.
I usually use one of the 74HCTXXX buffers for level shifting from 3.3V to 5V. They are pretty fast (~10ns transfer time), cheap, available in breadboard friendly DIP housing and readily available.
E.g. the [74HCT125](https://octopart.com/search?q=74HCT125&start=0&specs2.20.values=Through Hole) has 4 buffers, the [74HCT245](https://octopart.com/search?q=74HCT245&start=0&specs2.20.values=Through Hole) 8 buffers. You get them for about 50 ct.
Here some more information on interfacing 3.3V Arduinos to 5V optocoupled stepper drivers.