Well I have just purchased a collarless shirt from L M Lewin, so I'll let you know how I get on.
At £30, I though it was worth a punt
http://www.tmlewin.co.uk/Regular-Fit-Plain-White-Poplin-Tunic-Shirt/34097,en_GB,pd.html?start=1&cgid=Mens-Shirts&prefn1=collarShape&prefv1=Tunic
At £30, I though it was worth a punt
http://www.tmlewin.co.uk/Regular-Fit-Plain-White-Poplin-Tunic-Shirt/34097,en_GB,pd.html?start=1&cgid=Mens-Shirts&prefn1=collarShape&prefv1=Tunic