Hi nitro way,
the most popular 3 blade prop in the right size range is the Octura M435. This is available both unfinished:
http://www.offshoreelectrics.com/pro...Series+3+Blade
and finished:
http://www.offshoreelectrics.com/pro...octsb-m435%2F3
from a number of places including OSE, but is expensive and should really be paired with a brushless motor to get the best out of it - it is wasted on a brushed motor if that's what you still have.
A more cost-effective upgrade is the ProBoat stainless steel upgrade to the original plastic prop,
http://www.proboatmodels.com/Product...ProdID=PRB0154
as it doesn't need balancing and sharpening like to Octura copper props.
-yellow-bird