I know basically everything about this stuff (partner does not eat wheat).
So i would recommend to visit:
- ALNATURA shop in Zurich (close to Globus in town). They bake themselves and can have it even without yeast (hefe) on soda, ferment etc.
- MIGROS and COOP sell pumpernickel bread which is made of water, slat and rye flour, i.e. completely safe. MIGROS sometimes have even their own bakes rye bread (roggenbrot) as well, but you have to be lucky to find it, as not any Mirgros have it (the on in HB lucky to have).
- Any bio-shops would have it. There is EGLI in HB (downstairs you can eve ask for help, they will explain which is having what). Or Muller on Rennweg stress in town.
Whether you would like to have a tour with me, i would not mind.
Would you have any address for a russian shops in ZH, i never seen any!