Assuming server memory DDR3-1333, ECC and unbuffered... Three of the ones in the filtered link below should work (prices range). Ideally you should consult your motherboard manual for compatibility...
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007952+600006069+600006161+600006126&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&IsNodeId=1&Subcategory=541&description=&Ntk=&CFG=&SpeTabStoreType=&srchInDesc=
EDIT - saint19 beat me to the punch, but you see the theme developing...