I've found that in feed supply stores, the most readily available deworming product mentioned in this thread is Safeguard and Valbazen.
I see Wazine all over the place but, as it specific to only roundworms, it doesn't fit the profile.
Safeguard is always there, but quantity and form varies widely and so far I have only found Theison's to contain a bovine package of this dewormer in a large enough quantity to be used with a sizable flock of chickens.
Valbazen is sold in large bottles and is more expensive upon initial investment but, as mentioned in (I believe) page 2 of this thread, Valbazen is the best investment per capita.