have you tried googleing it? I don't know for sure but i bet wazine or safeguard(febendazole) would work. If not petsmart or a local pet shop might have some sort of wormer for cockatiels and parrots and birds like that.
foys pigeon supply, siegels pigeon supply, jedds pigeon supply the list goes on and on.
Your local feed store may have something called ivomectin, it's a cattle wormer but some people use it for pigeons. You'll have to figure out the dosage though.