You'll find some works of Sts Philoxenus of Hierapolis and James of Sarugh here:www.tertullian.org/fathers
The above site also has the works of other Syrian Orthodox writers, including Sts Dionysius Bar Salibi and Severus of Antioch (the latter's works being mainly polemical though). There are other translated works of these SO Fathers in the offline world; you should be able to find them at a good library.
The only other Syrian Orthodox writer whose works have been translated that i'm aware of, is the great polymath Mar Gregorios Bar Hebraeus. Nothing online though, as far as i'm aware.