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!