I'd start with the cheap, generic Chinese ones working at 433MHz. See how that goes and then upgrade if you find them lacking.
The reason why the Zeniko's fail is likely because they use the overcrowded 2.4Ghz band which is not just chock full of WiFi and bluetooth signals, but also sensitive to directionality and line-of-sight issues. 433MHz is inherently a little more robust, technically also simpler and generally less crowded.
The main problem some of the generic 433MHz wireless triggers suffer from is 'false positives'; i.e. they may randomly fire on spurious signals. But in my experience that's still a whole lot less annoying than false negatives where the flash doesn't trigger when it's supposed to.