So here is the markup:

<a class="hni_Button hnine_KioskBottomNavBtnIndexEN hnine_KioskBottomNavBtn" href="http://juniper:2107/Default.aspx?machine=NBI0EjQSNBISNBI0EjQSNA&session=Y3L3y-aj_023IS_R_Tth9w&contentid=4488001">

 What I want to do it this (but instead of the Id, I want to use the classname.)

public HtmlElement IndexButton
{
    get
    {
        return Page.Elements.Find("BtnIndex", TreatIdAs.Regex);
    }
}

Now I know I can do this to get the classname, but it only works with the full classname, not a partial!

 
        public virtual HtmlElement FindHtmlElementByClass(string className, string tagName, int timeoutInSeconds)
        {
            var findParams = new HtmlElementFindParams { TagName = tagName };
            findParams.Attributes.Add("class", className);

            return Page.Elements.Find(findParams, _defaultFindTimeoutInSeconds);
        }