Number of different options for a spool.
Speedtech RC make a steel one (which i personally use), although i'm not sure if they have any in stock at the moment.
Also, there are a number of aluminium ones around too, Jurgen and RCmainiax spring to mind, although again with limited avaliability.
Of course, if your really desperate for one, grab another front one-way pulley and outdrives, and either glue or pin them together.
Also, as your new to the 415, plenty of useful people with the car on the 415 thread, here: