It boils down to whether yu just need a trigger and will do the flash power settings manually or you need ETTL capabilities.
For both you can find several 3rd party brands with their radio triggers, just head down to the usual shops in Funan (as long as it is open) or other places.
There are starter sets (one sender, one receiver) and you can add receivers later if required.
Nowadays the Canon EX flashes can easily be replaced by cheaper 3rd party ones. I'm using the Yongnuo transmitter and manual flash and it exceeds my expectations everytime so much so my bowens has been underused.
If you insist on Canon the ST-E2 has been a classic and 'decent'