What's an effective replacement for an X-ACTO knife blade safety cap?

The safety cap for my X-ACTO knife blade has disappeared. I keep that knife in a drawer, and I don't want the blade to accidentally stab someone's finger or to damage anything else in the drawer.

A replacement cap seems to cost as much as a new knife.

What's an effective (and perhaps clever) way to cap the knife's blade so it doesn't accidentally stab someone's finger or damage other items in the drawer?

My hack with a similar knife (a scalpel which never had a cap) was to cut a short length of reinforced garden hose:

The natural curve of the pipe grips the knife and also prevents it from slipping through.