How about this?
http://www.intl.onkyo.com/products/accessories/ri-dock/ds-a5/index.html
Or if your budget extends further
http://us.marantz.com/us/Products/Pages/ProductDetails.aspx?CatId=ReferenceSeries&SubCatId=0&ProductId=NA11S1
(this has a built in DAC as well but also analog outputs)
http://www.intl.onkyo.com/products/accessories/ri-dock/ds-a5/index.html
Or if your budget extends further
http://us.marantz.com/us/Products/Pages/ProductDetails.aspx?CatId=ReferenceSeries&SubCatId=0&ProductId=NA11S1
(this has a built in DAC as well but also analog outputs)