Amazon has the Calvin Klein Men's Underwear Cotton Stretch 3 Pack Trunks for $26 with free shipping. List price: $43. Has good Amazon Reviews.
Amazon has the Levi's Men's Undershirts 3 Pack - Short Sleeve Cotton Crew Neck Tshirts for Men for $20 with free shipping on $25+ or with Prime. Breathable light and and made from soft 100% premium cotton fabric.
Has excellent Amazon Reviews.
Amazon has the Fruit of the Loom Men's Stay Tucked Crew T-Shirt 8-Pack for $13 with free shipping for Prime members or on $25+. Features 50% cotton, 50% polyester, wicks moisture, machine wash cold with like colors.