In Bexar county, the largest stock and variety of powder at good prices is always Bexar Community. They also have a large stock of Winchester primers priced just above average. They stock all shotshell supplies but no pistol or rifle bullets.
Don's on Fredricksburg. A place to shoot usually has plenty of powder. Patten Guns has a bunch. Taranis might have some. Best prices on powder will be Bexar community. Looking for pistol or rifle supplies?