This app was mentioned in 2 comments, with an average of 1.00 upvote
Specialized is ok (but doesn't show date): https://play.google.com/store/apps/details?id=com.specialized.watchface&hl=en
In addition to thick fonts, black-on-white is more readable too. I never found one so I made one myself: https://www.reddit.com/r/smartwatch3/comments/3aut6l/steps_to_make_a_watchface_optimized_for_sw3/