The fire extinguisher place off Airport near Lamar can do it. Don't bother with Air Gas, they've recently changed equipment and will no longer fill tanks 5 lbs. or smaller (or so they told me last week). And Austin Homebrew can never seem to fill your tank to capacity.
If you find any other options, please let me know...Air Gas used to be my primary fill site.
Then Austin Homebrew it is. There is a secret to getting them to fill your cylinder fully. Put it in your freezer the night before then the next day take it to them packed in ice, like sticking out of smallish cooler or insulated bag. It works every time for me.
"You are much better off with no numbers than meaningless ones. The minute you believe numbers uncritically, that is, without understanding how they're calculated and how well they measure whatever they're supposed to measure, you will generate a breed of employee who will produce numbers and not results. Your data-processing system will then serve not to describe reality but to lie about it."
Love the store but Homebrew is getting expensive. I'm not sure when their prices went up, but I used to be able to get my 10# filled for about $15. They're up to $3 per lb, $30 plus tax for a 10# tank is pretty crazy.