Help me please, I did lose the usb bootable

Hi,
I did install El Capitan, now i have the last version before Sierra. All works great!.
But I have a serious problem with it. In clover boot loader I have El capitan disk and the recovery disk.
I lose the files contained in the usb that I used to install El Capitan.
If I'll have problem with Osx I can't use the recovery disk without the usb.
What Can I do now?.
Is there a way for create a new bootable usb for my El capitan installation?.
Can you suggest to me a guide...for dummies. Thank...

Help me please, I did lose the usb bootable