http://www.bigalsonline.com has flourite 15.4 lb (7 kg) bags for $11.99
Shipping is $5.95 for up to $35.00, $6.95 for up to $50.00, $7.95 for up
to
$75.00 I've purchased a filter and powerhead from them before. I was
happy
with the service. They ship out of Niagara Falls, NY for U.S. based
orders.
I live in NY, and surprisingly, wasn't charged tax. I assume that all
orders from the US are not taxed, because they are a chain store out of
Canada. Hope this helps.

I think they have a different shipping rate for Flourite. The standard
shipping rate may not apply for Flourite. They add extra at the end.
Someone correct me if I am wrong. Anyway I sent mail to customer support.

Dominic