Need help: Postponing BRP collection date

Hi folks, I need some advice here.

My BRP collection date expires in a few weeks from now. I am currently in USA. My plan was to make a quick trip to UK, collect the BRP, come back to US, wrap things here in a couple months, and move to UK for good. However, currently there are lots of travel restrictions when you want to come back to US. Also, I need to get my H1B extension stamped at UK in order to get back to USA.

So, my question is, is there a way to defer the BRP collection date. Has anybody done it here? Could you please share any info, either from your experiences, or from any relevant documentation?

Thanks in advance!

Bubun