You're pretty much stuck with what you've got. You could certainly find a shop to build a custom turbo setup but it would cost a lot. More than trading in for a V6 and who knows how much boost the stock components could handle before you'd need to pay to upgrade them, as well.
I feel your pain though. Back in the day I had a I4 2002 Mitsubishi Eclipse that was painfully slow. I ended up running a Zex Nitrous kit until I was able to find somebody selling custom header manifolds I could source together the rest of the parts for a turbo. In the end, I wasted a lot of money and it wasn't worth it.
Current: 2016 KL Latitude V6 ADI
Past: 1997 ZJ, 2003 WJ, 2007 JK