Measure it. Sculpt it. :)
There is an expanding resin that you put into water to swell up. But it works best in a spherical object. This involves making a rubber mold of the original and anther one of the bigger copy. And it will take many copied to get a significantly bigger model. You could easily pay $2000 for matierial alone.
Another way is to Cyberscan it and have it milled out in a different scale. That will cost a couple of grand too.
You can download a great 3d mesh off the internet and cut from that. Or generate plans from it.
There is no easy way to do what you want. What you want to do is scratch build the size you want.