Even my cousin needed one for his WFH, but no where router UPS is available.
So, I have given him my CyberPower 1KVA UPS with new batteries installed.
I think it should be able provide backup for atleast 3-4 hours.
You can check Acer Aspire E15 (E5-576).
i5 8th Gen
4GB DDR3L RAM (will be sufficient for your needs. You can always upgrade your RAM later.)
Add Acer's (2 Year) warranty extension pack for Rs.500.
I had purchased his for 32k around 2 months back from flipkart.