Hull and hardware is a good option, usually electronics and motor they cheap out on. What size shaft does it have on it? Octura, prather and grimracer propellers are all imperial shaft sizes and have a huge selection of props, 1/8 is used for smaller stuff, 3/16 probably has the widest selection of props, 1/4 is for the big guys. The metric sizes are becoming more popular and I believe adapters are available, although I very well could be wrong on that one! You can use a bit of brass tubing to shim down a 3/16 sized prop to fit a 1/8 shaft.
It may be overkill but I use 3/16 on just about everything, mostly because I already have a selection of props in that shaft size.