Here's mine[1]. I need to button it up for an actual release, and improve the demo to show more options... it's pretty flexible and the modal is entirely standalone, with no external dependencies on the built version.
You could write a pretty thin shim for wiring up date inputs. I didn't write an actual date input component as I wanted it to be able to tie to whatever input component/method one wanted... but have a nice full-modal picker.
Also, as you resize the screen it will handle reflows/sizing as well as vertical scrolling when the window is too small, many modal templates won't do that properly. The size min+gz is about 20kb, using preact, preact-compat and redux... I'll probably refactor to separate the actual date-picker component from the modal, and make it more friendly for use inside react (and preact-compat) projects, without the bundling.
edit: the demo doesn't always seem to gzip the js, it's about 60k non-gzipped, but can shrink a bit with gzip level 5-9 compression.
[1] http://tracker1.github.io/md-datepicker/