please help me figure out what kind of fins to get for this

I got this board real cheap, filled all the dings with a repair compound and now I want to get some fins-cheap.
The screw hole is in the front, the length of the groove is 5.5 inches. the distance between the center of the screw hole and the beginning of the groove is about 1/4 inches.
Been looking online,mainly ebay, can't figure out. Nothing looks like it would fit. I wanna spend as little as possible.
The screw hole is in the front, the length of the groove is 5.5 inches. the distance between the center of the screw hole and the beginning of the groove is about 1/4 inches.
Been looking online,mainly ebay, can't figure out. Nothing looks like it would fit. I wanna spend as little as possible.