Creating a custom (and free) CalTopo layer with Sentinel imagery?

I’d like to help create a custom (and free) CalTopo layer with Sentinel imagery.

To start, I’d go to CalTopo dot com and select “Add/Custom Source”.

I then need to add 1 or 2 URL’s for “URL Template” and/or “Auto-Configure URL”.

As an example, here is a CalTopop map with a custom layer that has snow-depth estimates. Default Map

The “URL Template” for the custom “Snow Depth” layer is:
Export Map (NWS_Observations/NOHRSC_Snow_Analysis)},{right},{top}&bboxSR=102100&imageSR=102100&size={tilesize},{tilesize}&f=image

Is there a URL such as this I can use to create a custom (and free) CalTopo “Sentinel Imagery” layer?

Thanks!