"The Commonwealth doesn't have one, India has one.
If you ask nicely and permit increased immigration they might let you join in... but it is a regional system with coverage of the area containing targets for their nuclear missiles."
The current IRNSS system is indeed regional. It was conceptualized after GPS access issues during the 1999 Kargil War. Budget allocations started 2006, and satellite launches started in 2013.
It became operational in Spring 2018 with the launch of the 7th satellite IRNSS-1I in April, and covers India along with an area extending 1500km around it. The total cost so far is approx $340 million for the project, 7 sats and launchers (PSLV-XL).
It will be expanded to a global network of 24 satellites, probably by the mid 2020s.