Is there a Walmart near you? Silly question, I know.
Repel makes a Permethrin product that Walmart sells in the camping section. Most folks report noticing no difference in the effectiveness and I would tend to agree. Only thing I've noticed is that the treatments don't seem to last as long as the Sawyer spray treatments. If it were me, I'd go get a couple of cans of that for the current trip, then order the soak method from Sawyer online and have it for the next adventure.