It appears that it may be possible in the near future for G-20 travelers to India arriving at BOM, BLR, and DEL to get some sort of a prepaid debit card or mobile wallet loaded with INR to use for UPI transactions in India.

https://www.thehindu.com/business/rb...le66537286.ece

https://www.devdiscourse.com/article...om-g20-nations

How convenient this is may well depend on how easy it is to get this set up at the airport, and how easy it is to get a refund of unspent INR on the way out.