Only problem but every photo of a member of Sudetendeutsches Freikorps I've seen Wears civilian cloths and a helmet, not the full getup.
The Bulgarian officer second right in this photo almost has the correct tunic. The tailoring of those tunics will be key, concealed buttons and pockets, slightly scalloped pocket flaps with a bright button.
That`s why I said "maybe on the lines of." I`m no expert on these things so just throwing a few ideas out there ? The photograph `appears` of a later period (Than immediate WW1) hence the `Sudetendeutsches Freikorps 1938` reference ? The soldier with the `eagle and wreath ` insignia indicates post 1933 but the tunics in your photo appear earlier .. Kyle