One: Google, or check the links here for Goex, and look at their map of the US to find the distributor for Texas. The map will give a name, phone number( 800) and/ or an email address. If you contact the Distributor, he will tell you where your nearest retailer is located.
Two: If there is no nearby retailer, he will get you the powder you need to you. Find some friends to place a joint order. Most dealers and distributors will allow you to mix an order- order both ONE CAN of 4F powder, and at least 4 cans of 3f or 2f powder, for a minimum order of 5 lbs.
If you order this from Powder, Inc., or Graf and Sons, (again, see the Links at the Member Resources at the top of the Index page to the forums) they will pay the shipping, and simply charge you the $20.00 haz mat fee.
The Haz Mat fee is $20.00 per shipment, so the more powder order, the less that fee is going to be per pound ordered. It pays to find a group of men to place an order, so that you all reduce the cost. There is a savings to be had ordering by the case( 25 lbs) rather than in a smaller order, but the smaller order will still be cheaper than what you will have to pay at retail. If you have a friend who is also a flintlock shooter, split the can of 4F powder with him, BTW. You can received up to 50 lbs. of powder per shipment, which would be two cases.