Clickers have long been out of production and for a good reason, they are an inferior product when compared to today's binders.
You'll have to look on Ebay and craigslist. If the boots you have have the internal highback than just get the plates. Otherwise, I guess you'll have to look around until you find some with the highback.
Also, you could just get a binder like Flow's if you are looking for the quick convenience of step in's.