I wonder whether you chose the proper size of your e-bike?*
It is nothing wrong with raising the stem if you need to ride more upright and understand the consequence of riding in a more relaxed position. I was using stem risers myself until I understood it was the wrong way (for me).
You can use any 1-1/8" stem riser, such as this one:
The setup is very easy, and you can use the provided spacers to set the stem rise freely up to 78 mm (it is
a lot!) The only thing you should be careful about is that the top of the stem (or a spacer above it) is really aligned with the top edge of the steering tube, so the cap is slightly compressing the assembly downwards after you have tightened the main long screw.
As I said before, I had been riding with stem risers on any of my e-bikes for almost 3 years, and I only started wondering whether that was the right decision when I read posts of people such as
@mschwett (who advocated for narrow & firm saddles; and he rides a lot!), and thought of reducing the air drag on my rides. Then my rides changed to be beautiful and painless. (More aggressive riding position than it was originally designed for those e-bikes!)
*) My brother owns my former e-MTB in size M. He is a tall person (far taller than I am). If he tried to ride that e-bike as designed, his head would be located below his butt! So yes, he has a 75 mm stem riser installed for a proper riding position, which is still aggressive for him! But that is just because of the wrong e-bike size!