Turn Signals have been discussed on this forum and many other old car forums in the past but a new product is on the market which might be of interest to people. A person on the Model T forum mentioned it and it looks like a well made product. It doesn't solve your problem of what to use for lights but it looks like a high quality controller. The web site is WWW.turnswitch.com Maybe someone can use this information and report on it.
Thanks
Jan