Select Box designs, themes, templates and downloadable graphic elements on Dribbble
A Bootstrap / jQuery based select box with search and multi-select options
Bootstrap Select Dropdown with Search Box — CodeHim
html - How to reduce dropdown box width in the select box - Stack Overflow
GitHub - PhilippeMarcMeyer/vanillaSelectBox: A dropdown menu with lots of features that takes a select tag and transforms it into a single or multi- select menu with 1 or 2 levels