A quick Google search on  "bootable utility disk" or "bootable rescue disk"  or "bootable antivirus" will get you quite a few good suggestions.  Normally you would need a separate USB for each one.  You might also look into:

http://www.easy2boot.com/download/

Easy 2 Boot allows you to have more than one image on a flash drive.  Their website is horrible though.  It isn't hard to use, we can look at it in class.

Here is a link to a good article

https://www.thetechmentor.com/posts/10-great-tech-tools-boot-cd/