Cabelas has a couple of them.
http://www.cabelas.com/cabelas/en/te...eter&noImage=0
http://www.cabelas.com/cabelas/en/templates/links/link.jsp?id=0047111019319a&type=product&cmCat=Sear ch_Results_NYR&returnPage=search-results1.jsp&QueryText=oxygen+meter&N=4887&Ntk=Pro ducts&Ntx=mode+matchall&Nty=1&Ntt=oxygen+meter&noI mage=0
Jeff