Is additional fastening material meant here?? Unfortunately, I don't have an answer.
Screws for HDDs should work as a replacement. However, the HDDs protrude quite far into the enclosure because of the hole positions (see below).

Otherwise, fastening elements (see picture of the unit 4th button, side opening) are supplied (for 2 x 3.5" and 1 x 5.25") These elements have pins that fit into the HDD screw opening. The middle, rotating part of the elements is a bayonet catch, 90° rotatable.
- These elements fit CD-ROM drives very well.
- HDDs, on the other hand, protrude quite far into the enclosure.
- SSDs need the adapter U-sheet for 3.5" and then the fastening elements fit well.
All the components are a little loose because the elements only hold them and do not tighten them like screws.

Since HDDs stick out too far into the case for me, and I only use the Cooler Master standing up without much transport, I fixed my HDD with only one screw to get it into the desired position. The rest of the HDD rests on brackets that are in the bay.
The enclosure is not necessarily made for many HDDs. SSDs with adapters fit well.

Greetings

Thank you for the good advice.