There’s also no reason why you couldn’t use nesarim, narrow slats of lumber/wood, for sechach. The Gemara mentions these explicitly. These would be a lot cheaper than buying a bamboo schach mat with hashgacha. Rambam, Hilchot Sukkah 5:7, says:
“Boards which are less than four handbreadths wide may be used for sechach even though they have been planed. If they are more than four handbreadths wide, they should not be used as s’chach, even though they have not been planed. This is a decree [instituted] lest one sit under a roof and regard it as a sukkah.
If one placed a board which was more than four handbreadths wide over [a sukkah, the sukkah] is kosher. However, one should not sleep under the board. A person who did sleep under the board has not fulfilled his obligation.
There were boards that were four handbreadths wide, but less than four handbreadths thick. A person turned them on their side so that they would not be four handbreadths wide to use them as s’chach. This is not acceptable, because a board is unacceptable for use as s’chach whether one uses its width or thickness.”