Can anyone tell me the name of this knockoff transformer combiner?
You're probably right. There are tons of generic robot toys out there, especially ones based on popular designs like construction vehicle transformers.I'm pretty sure that's just one of those generic Chinese combining robot toys.
Like if you look up 'transformer construction vehicle' on Amazon, you'll find multiple different versions of those same molds being sold by different sellers.
Probably does have an 'original' version somewhere but at this point if you can find what rando Chinese company originally released it, good luck.