tamiya does not make a spool, but it is very easy to make one your self.
all you have to do is...
1. obtain some aluminum oxide sandpaper(a medium grit will work)
2. use a spare or used diff ring and trace the shape onto the back of the sandpaper. do this a total of 4 times.
3. cut out the new sand paper diff rings.
4. double up the pieces of sand paper and glue them together (this will achieve the correct thinkness of a metal diff ring)
5. glue the new doubled up paper diff rings to the black ring holder of the outdrive.
6. wait for the glue to dry, and then just re-assemble the diff together leaving out the diff balls, then tighten the diff nut down all of the way and this will allow the sand paper to bite very hard onto the gear.
i ran the spool setup as described above for one month on carpet with foam tires, and did not get even one slip out of the spool.
i got this idea from the spool pads that come with the new team losi graphite plus xxx-s kit, except i think that my design is better because when running the 414, if you break a plastic outdrive, or wear out a steel one, all you have to do is replace that particular portion becuase the black ring hold stays intact!
p.s. if you need a picture of what i have described above, let me know and i can post one real quick.