They're from an Australian company called Pepeny, which is the Aboriginal word for hoop skirt. From what I see, they're available everywhere.
Now, I understand the importance of protecting kids from the sun, especially infants. Every time a ray of sunlight passes over my kid's exposed calf, I pull down her bunched up pantleg. But honestly, I wince more in anticipation of getting chewed out by some busybody with a party tent pitched on her stroller than for the kid getting a little UV exposure.
Buy a Pepeny if you must for $39.99 at buybuybaby.com.