Merging two iCloud back-ups or contacts?

Dear community,

My phone was stolen recently and I am thus using a secondary phone that is based on a back-up from my other phone from a few weeks ago. Since it’s storage is smaller, I already made some adjustments and thus cannot install the most up to date backup of my stolen phone.

I noticed that many of my contacts are missing. I am a bit surprised because contacts are syncing as part of iCloud so I would assume that new contacts would be automatically downloaded to my secondary phone. Is there any way I can access my contacts and make them available on my secondary phone? If not, is there any way how I can get access to the contacts from the iCloud back-up from my stolen phone without installing the full back-up?

Thanks in advance for your help!