For thicker PEI that comes with adhesive, I got one here by emailing email@example.com and requesting a 40mil thick 170mm x 170mm (that’s the size of the glass for a Mini). They custom cut one for me and had it out quite quickly and the price was reasonable.
There are some threads here detailing replacing the PEI. It’s pretty easy. Put the bed in the freezer for about 15min, pull the PEI off. Then use adhesive remover and a razor blade to remove the adhesive. Now thoroughly clean the adhesive remover from the plate. I used windex to clean everything, then alcohol as a second pass to make sure. Don’t forget to wash your hands as well, everything needs to be very clean. Then peel and stick. I went slowly from one side pressing down with a plastic putty knife as I went to try to get it as flat as possible. The added thickness helps here, it wants to be flat.
Now, when re-installing the bed the spacers on the corner washers are just a bit short. I put a #6 washer under each one to space it up a little to account for the now thicker bed. Don’t force it, one user has already reported breaking the bed tightening too much. I press the bed plate down with one hand, while tightening the screw till it’s snug. Just enough to hold it all in place.
Now do some tests starting with a Z-Offset of about 0.1mm. That starts things a bit high, you then need to dial it in based on filament and how much “squish” you want on the first layer. Nylon might need to be closer, PLA will stick if it manages to touch the bed.