Using regular expressions in CSS selectors
See here for the original answer.
One way to achieve what you are looking for in pure CSS is with an attribute prefix selector (which uses a form of regular expressions). In your case the following would likely do the trick:
[id^="edit-field-geolocation-proximity-center-geocoder"] .form-item {
/* your styles here :) */
}
This thread offers a lot of additional excellent methods on how to use regex in CSS if you would like to do some additional reading.