EDIT: Misunderstood what you were asking a little. Here’s a better answer.
You could achieve this pretty easily by upscaling the 16x16 assets (there are 16x16 and 48x48 included in the pack) by 2x. You would want to use “nearest neighbor” settings to avoid distortion. These assets already use solid black outlines, you could in most cases simply paint bucket the black to white for selection UI stuff. There may be a few examples where this wouldn’t work but would require minimal editing to fix.
If you don’t have the know-how to do this, I can put together an update that includes both 32x32 versions AND white outline version. No one’s ever asked for this before but more options can’t hurt. I should probably just do it anyway.