Well, either D&R Marine or Cape Cod Shipbulding is best if you ever think you wil lrace the boat, since they sell the Class-Approved rudder. D&R sells the original one for the DS II/Javelin, so you won't need to change fittings. OR you could make one? Day Sailer Class web site has the dimensions
www.daysailer.org
Incidently, as you may note from my description, the Javelin used the same rudder, so that expands the used rudder option. I addition to the safety pin that Joe mentions, a lanyard between rudder and boat is not a bad idea given the weight of a DS II rudder.
One other tip....... don't capsize again?? ALWAYS hold the mainsheet in your hand while sailing, let the camcleat hold the tension, but keep the sheet in hand to allow spilling the wind when a puff hits, I've used that technique to stay capsize free for 25 years of centerboard boat (7 years with a Widgeon, 18 with a DS II) sailing. Had water start to come over the side a few times...... but, let the mainsheet go to spil lthe wind and she come back upright (and you can catch your breath!).