You can find lace fabrics at Jo-Ann's, Fabricland, FabricMart, possibly Hobby Lobby --- anywhere that sells fashion fabrics. (Especially if they handle finer fabrics for weddings etc).
The corduroy should work fine with quilting cottons..... just be aware of the difference in weight. There are some very nice light-weight cords out there, especially for kids, but also some that are very heavy. You may want to prewash your fabrics if mixing types, as I'd expect the corduroy to shrink at a different rate than quilting cotton.