After various manufacturers (Hermko, Schiesser, Albert Cross, Hanro etc) did not come into question because of the P / L ratio (30.00 to a whopping 120 !!! for an undershirt is beyond my imagination quite properly), I'm back at " landed American T-Shirt "by Tommy Hilfiger.
15 per shirt regular price, 10 per shirt at a reduced price: are absolutely ok.
The delivered for quality may not be enough to Zimmerli Herran, but for my needs I get a dense matrix algebra equivalent and my search ended successfully.