Does anyone have any suggestions for a reliable online dealer who has DAK tunic(s) for sale from time to time? Thanks.

All of them
Bill Shea: http://www.therupturedduck.com/WebPages/Sitemap/sitemap.htm
Peter Hammond: http://www.germanmilitaria.com/Covers/Germancover.html
Helmut Weitze: https://www.weitze.net/

Maybe not at the moment, but you have to check in regularly as they get those.

Thank you, Herr Wolf.