Xamarin Forms Slider With Custom Thumb

I am trying to make a custom SliderRenderer for Xamarin.Forms that can allow me to change the thumb to be in image instead of just a circle.

On native Android I found you can do something like this:

Drawable myThumb = getResources().getDrawable(R.drawable.slider_button);
myThumb.setBounds(new Rect(0, 0, myThumb.getIntrinsicWidth(),myThumb.getIntrinsicHeight()));
skbr.setThumb(myThumb);

Link to source: http://stackoverflow.com/questions/3882992/how-can-i-change-the-android-seekbar-thumb-drawable-after-oncreate-method

I don't know how to get an image or resource properly with Xamarin Android though. Anyone know how to handle this?