If you should need to replace the handle with something else entirely, rather than just restyling it:
$('.slider').append('<div class="my-handle ui-slider-handle"><svg height="18" width="14"><path d="M13,9 5,1 A 10,10 0, 0, 0, 5,17z"/></svg></div>');_x000D_
_x000D_
$('.slider').slider({_x000D_
range: "min",_x000D_
value: 10_x000D_
});
_x000D_
.slider .ui-state-default {_x000D_
background: none;_x000D_
}_x000D_
.slider.ui-slider .ui-slider-handle {_x000D_
width: 14px;_x000D_
height: 18px;_x000D_
margin-left: -5px;_x000D_
top: -4px;_x000D_
border: none;_x000D_
background: none;_x000D_
}_x000D_
.slider {_x000D_
height: 10px;_x000D_
}
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>_x000D_
<script src="https://code.jquery.com/ui/1.9.1/jquery-ui.min.js"></script>_x000D_
<link href="https://code.jquery.com/ui/1.9.2/themes/base/jquery-ui.css" rel="stylesheet" />_x000D_
<div class="slider"></div>
_x000D_