Upvote:1
According to this travel planning website, there are no non-stop buses that go from Panama City to Rivas, the only bus option has one stop in San Jose. The only non-stop option - at least presented by this website - is to drive.
Upvote:2
Rome2Rio shows there is a bus Panama City - San Jose, Costa Rica twice a day and San Jose, Costa Rica - Rivas five times per day. The first one should cost 50 - 95 USD, second one 30 - 45 USD (in total 80 - 140 USD). First one takes 16 hours, second one 6:30 hours.