Texas Pride BBQ in Adkins
I have never had any german potato salad there,just regular, but i'm sure they make it.You can check their website to see if they have it.
Schilo's deli downtown in SA might have it. Most of the potato salad I've had around here has been regular potato salad.There is a german restaurant in New Braunfels called I think Frisian Haus,located in the old Krause's Cafe that may have it.
They also have Friday Night fish fries and music then, but with the approach of winter they usually stop and resume in the springtime.