Like univland said, in Lawrence is where I get them, pretty much any where down river from the Lawrence falls. Make sure you have some heavier lead free weights to add to your line. Some times the shad are down deeper and the tin darts won't be able to get down there with the fast current.
I sell bismuth darts which are much heavier than pure tin. But probably cost more than what you paid for yours.
Check them out at
www.suckerpunchbaits.com