The best thing I have bought for my dinghy Nessy is a pair of square rowlocks, very like the ones in both the pre-war Snarleyow boats in the previous post.
Round rowlocks make feathering the oar very hit-or-miss, and getting it wrong can result in you lying on your back with your legs in the air, like Ratty. And I have never liked the feel of the round oar wobbling in the round rowlock.
Square rowlocks hold the oar firmly in place, either horizontally or at the correct 6 degree angle to the water, so you can put the power on with confidence.
Nessy's square rowlocks are things of beauty, created by American sculptor Doug Martin. They are cast in manganeze bronze, with nice big flats to take the pressure and horns at the top to hold the oar in safely.
I got them from Duckworks at an incredible $50 the pair. Similar items in the UK are £50 each - at current exchange rates that is four times the price. At the moment, getting stuff shipped in from the US can offer huge savings over your local chandlery.