This is the official Microsoft download page for Windows 7:
https://www.microsoft.com/en-gb/software-download/windows7
However, OEM Product Keys (those supplied with pre-installed Windows) may be rejected as support for OEM Windows installations is the responsibility of the PC or laptop manufacturer, not Microsoft. That's why the OEM manufacturers
provide a utility on your laptop which allows you to make a set of factory recovery discs to restore the entire OS if necessary.
In the event your Product Key is rejected (no download possible) your laptop manufacturer may be able to supply a set of Recovery Discs for your model.
It has to be said in all honesty, you should have made a set of recovery discs yourself (or created a disk-image) before you removed Windows 7, . That would have avoided your present predicament.