Well you could spend 10s of thousands on a real Grand Piano, and pay for a Piano tuner to retune the instrument every time you moved it to a new Gig, or you could pay a few hundred Pound/Dollar/Euro for a VST and load it into a Laptop (If your still using a Hardware Arranger) or if you have a Wersi OAS Instrument or Mediastation, load it straight in, and use and play it as if it was a normal voice. (Just think your playing a Grand Piano with other Grand Pianos in your styles)
Another option is to purchase a Hardware VST player (Such as Receptor) and link this to your Keyboard.
Enjoy whatever you play

Bill