I'm not in a position to offer code this weekend but the check-boxes are ::before and ::after pseudo-elements affiliated with the labels. Changing the margins, width, height and font-size of those pseudo-elements should do the trick.
Cheers,
Tony Partner Solutions, code and workarounds presented in these forums are given without any warranty, implied or otherwise.
Could be close enough--but I'm getting a slightly different result than you (see attached).
The check marks are not centered in my rendering but rather placed towards the bottom of each checkbox.
I wonder why the difference. Is there something that controls the placement of the checks in the checkbox?
I tested by making a copy of the default template and adding your lines at the bottom of template.css.