Probably some of the Cryptocoryne, such as C. beckettii, C. walkeri (lutea) or C. wendtii, can hold their own under those conditions. The old fashoned large amazon swords, Echinodorus amazonicus or E. bleheri are also quite tolerant of low light. If you can get it, try Hygrophila polysperma. If that can't grow, then you are really limited to the lowest of the low light plants, such as Microsorum (Java fern) and the above Crypts. . If H. polysperma can grow, then probably Bacopa carolinia can, too.