I think the original suggestion was the best you are going to do, an HD4650. Unfortunately the DDR3 version of the card seems to have become rare and I'm not seeing it in low-profile anyway so I guess you'll have to get the DDR2 version;
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010380048+106792627+1419531894&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&Subcategory=48&description=&Ntk=&CFG=&SpeTabStoreType=&srchInDesc=4650