i usually order 5-10 of them and that helps offest the $3 shipping charge.
http://www.ebay.com/itm/Latest-HPI-76937-Spur-Gear-47T-Savage-25-Savage-X-X-4-6-/181560434147?pt=LH_DefaultDomain_0&hash=item2a45d85de3
That's exactly what i would do.
So many things break i have just kept it mostly...
i am running a 19/47 but i like anything from 17-19 on the clutch bell. Buy a hardened clutch bell gear or you'll be shredding the stock one real soon with that steel spur gear. Steel ones are stronger but i like the $3 price tag of the pastic ones, at that price i'll shred them all day long :)