Enter non-breaking space without a numeric keyboard pad?

Fn key

The Fn key generally works only with "alternate" keys. On some keyboards, this includes an alternate number pad as shown below. You can try this on a laptop without these markings on the keyboard, but that may not work.

Character Map

One option is to copy and paste from the Character Map. That removes your dependency on an external keyboard, but that means you can’t use your clipboard at the same time.

To access the character map, click the Start button, type Character Map and press Enter. From there the non-breaking space is in row 5, column 15. Click that cell, click Select and click Copy.

Autokey

Another alternative is to use AutoHotkey and the following script:

#s::
Send % Chr(160) ; code for the non-breaking space

This would send the non-breaking space character any time you press Win + S. You can replace that shortcut with whatever else you like

But does your keyboard have a Numlock key and numbers on the 7/8/9/u/i/o/j/k/l/m keys? (Assuming Qwerty layout)

Engage Numlock then use these keys for the ALT combination. (Note that the 'm' key is used for 0, not the zero key.)

Note that the Numlock is probably a function key combination: on my Samsung keyboard it's Fn+F11.

For occasional use the Character Map copy and paste method may be easier.