All the signs are that we won't be able to get them from our suppliers. :( Via the following link you will find alternatives that may possibly meet your needs: https://www.galaxus.ch/fr/s7/producttype/emballage-alimentaire-2578?filter=t_23282%3D979918 However, we did not find any clips ≥ 20 cm.

These have a clamping length of about 18.5cm (so they are about 19.5cm in total). As far as I know, these are the largest ones. The medium sized ones have a clamping length of about 9.5cm and the small ones about 6cm. If it is not enough, e.g. for large chip bags, you can also fold it up at the top to make it fit.