There are two shops in Martinsburg.PA which are about 30 miles from Altoona. The two shops are only about 5 minutes from each other.
The first is Country Beefers . Coming from Altoona will be the first shop of the two you will come to. Small shop with a lot in it. They don't have a website but can get directions to both on line.
The second is Traditions. Restaurant decorated with quilts and other neat objects. On the other half of building is quilts, materials and other sewing things. Kill two birds by eating and shopping here.
In Altoona there is Joanne Fabric, Surplus City (Material not real good quality) and a Walmart.
Hope this helps.