Flexbox alternative for IE9

I have developed a website with Chrome initially (easiest to design for) but now am getting to IE support model.

That being said, I started with IE11 and made the necessary changes for the quirky differences between IE & Chrome. But now I am stepping down the IE versions. I was able to get 90% of the webpages to display correctly with CSS for IE10. But now most of the CSS elements that I have for these two browsers, are for the most part irrelevant for IE9.

I would like to keep from needing to have multiple browser specific style sheets, if possible.

First problems is converting IE10+ implementation of the flexbox model of CSS.

Current Implementation for the flexbox container:

div#navContainer{    display: flex; //Current browsers (IE11, Chrome, etc)    display: -ms-flexbox; //IE10 implementation}div#TeamsSection {    text-align: center;}div.NavSection {    margin: 0px 7px;    padding: 4px 0px 0px 0px;}div#teams {    margin: 0px;    select {        margin: 0px;    }}

HTML:

<div id="navContainer" class="float-left"><div id="LogoSection" class="NavSection"><div id="Logo"><img src="Images/Logo.png" /></div></div><div id="TeamsSection" class="NavSection"><label>Select a Team:</label><br /><div id="teams"></div></div><div id="UserSection" class="NavSection hidden"><label>Select a User:</label><br /><div id="requestor"></div></div></div>

I know IE9 does not implement Flexbox, so please don't insult the research I have already done. I need an equivalent implementation that will allow me to change the HTML as little as possible.