There are many, many suppliers of inexpensive Bag-Valve-Mask kits. (That's the whole reason for the interest in using them.) Rather than trying to provide complete documenation on all the the possibilities, I will just provide a few random links here.
https://www.redcross.org/store/disposable-bvm-bag-valve-mask-adult-size/760002.html
https://www.redcross.org/store/disposable-bvm-bag-valve-mask-pediatric-size/760001.html
https://www.ambuusa.com/products/airway-management/resuscitators/product/ambu-spur-ii
https://www.aedsuperstore.com/ambu-bvms-bag-valve-masks.html
https://www.boundtree.com/Airway-Oxygen-Delivery/Bag-Valve-Masks/c/20
https://www.buyemp.com/category/breathing-respiratory-equipment
https://www.aedsuperstore.com/resources/bag-valve-mask-bvm-guide/
https://www.mcrmedical.com/documents/38/BVM-Manual%20with-Copyright.pdf