Cmlt via Amazon offers its Cmlt Men's Long-Sleeve Cotton T-Shirt in several colors (Army Green pictured) for $18.99. Coupon code "LMVW375Q" drops that to $13.29. With free shipping for Prime members, that's $6 off and the lowest price we could find. Its available in sizes from S to XXL.

Note: Army Green in size S drops from $12.99 to $9.09 via the same code.