I know what a push-in wang bar is. All my Wilkinsons have them. What I don't know is what it is you're asking. Do you want to know who uses that design? Wilkinson, for one.
Others do it as well, but only few people actually make them. You'd have to get a model number and look it up. Most OEMs like Fender, PRS, Ibanez, et al just have somebody like Ping (China), Gotoh (Japan) or Schaller (Germany) make their bridges for them, and most of them are based on the Wilkinson (UK) design unless they're trying to emulate a Floyd Rose or one of the crappy old vintage parts. That makes it tough to say what to expect.