All the replies above are too expensive, by far. The sprayer is ok, the head is ok, it's the "O" rings in the head that are worn.
For the uninitiated, "O" rings are rubber bands that keep taps and spray heads from leaking. The "O" ring allows the spray head to turn round and round without leaking.
I recently repaired my toilet spray. Price of replacement from the RV store $48. Price for replacement of "O" rings from Ace Hardware $1.41 plus tax.
In the toilet (or sink) sprayer are three "O" rings. Unscrew everything and you will find them. Lever them off, and take them down to Ace Hardware, or any other good hardware store. Match up the rings with the pictures of new rings on the "O" ring display.
And when you have replaced them and put everything back together again, you will feel so Goooooood!!
Rankjo