Help! Love my tabi shoes but they’re too big. Any way to fix it?

I got a pair of tabi flats and I really love how they look, but they’re too big. I already have the smallest size (EU 35), so I can’t size down.

I’ve tried wearing thick socks, and that helps with the fit, but then the back cuts into my heel—probably because my heel isn’t sitting high enough. I also want to be able to wear them without socks.

I think the main issue is that they’re too long, and my heel needs to be a bit higher. Would heel pads help by lifting my heel and filling some of the space in the back? Or should I just give up and return them?