I order mine online. I get a custom blend from Uckele Equine Nutrition. They also have off the shelf products. Horsetech.com has a great product called High Point. Their prices all include shipping.
Is your horse only on pellets, or does she get hay as well? If she gets less than 8lbs of alfalfa pellets daily, then you do not need an alfalfa balanced vitamin supplement.
ADM has a good product called StayStrong Metabolic Minerals. It has GroStrong minerals plus added vitamins to balance a horse's diet without the use of grains or feeds. I used it for a while with good results, but it was hard for me to get. I don't have a local store that sells ADM products unfortunately.
It looks like there are three different stores near you that carry ADM products. You might call them and ask if they have StaySTRONG or can order it for you. It's very affordable to feed as well as you only feed about 1 lb a day per-horse.
MCDONNELL BUILDING MATERIALS C
600 N MAIN
KELLER, TX 76248 10 miles
817 431-3551 mcdonnellfeed@gmAil.com
ALVARADO FEED & SEED INC
1209 S PARKWAY
ALVARADO, TX 76009 26 miles
JOSHUA FEED STORE
520 S BROADWAY
JOSHUA, TX 76058 27 miles
817 558-3444 firstname.lastname@example.org