DIY

I do not recommend using new one-way-bags. They are expensive, and there's plenty of material around that we usually throw away to end up in a landfill. There are a few bags that are (at least in Europe) marked with that triangle-symbol with a number 5 inside and the letters PP (polypropylene). Often bread comes in these bags. There is also rectangular food packages made of this material, and buckets. All of these can survive the pressure-cooker, or can be filled with steaming hot pressure-cooked substrate, and that's good enough for oyster mushrooms.

I'm still unhappy about all the pressure-cooking, and have been looking into using wood ash for pH-pasteurization (was that the word?). Can't say I had much success so far, but might try again in the future.