Gorgias and Eisenbrauns have teamed up to publish an updated version of Brockelmann's Syriac Lexicon (edited and updated by Michael Sokoloff). I haven't had a chance to use it at length, but it looks wonderful, and as I've handled it I'm sure that it's worth the money that I've spent on it. The text entries are in estrangelo, sometimes pointed (in contrast to Payne-Smith which presents the entries in serto, but has the guide words at the top of the page in estrangelo).
Many thanks to Dr. Sokoloff, Gorgias, and Eisenbrauns for your work. Syriac reference tools aren't high-traffic items, so blessings on you!