I have put some dinghy bits on eBay. Some suitable for a Merlin Rocket including combi trailer, Milanes rudder a nice proctor boom, came of a firefly but would be ok for a Merlin. 

Also laser dinghy and laser bits, firefly mast, cover, boom as well as Nat 12 bits. 

Search 'Milanes Rudder' then go to 'sellers other items

All items starting at 99p