I don't see it mentioned in this thread, and I don't know this first hand, but have seen
claimed elsewhere on CPF that Sunwayman has some E Series thread-compatible parts, namely, the V11R, which is itself designed to be backward compatible with all the earlier M- and V- series lights, (so they should be E Series thread-compatible also?).
Also I have seen mentioned that Sunwayman parts just barely give enough threads to keep parts threaded together, and that V11R has a nasty magnetic drift (manufacturer's claimed regulation is apparently only anacdotally a specification). V11R's have really come down in price, and if not for the widely reported magnetic drift, I'd have pulled the trigger by now. No one wants to give negative reports, and that's nice, but we sort of need to know, negative experiences or not.