Probably best to goto a local exhaust place and have them make you one.
Or buy a 1.8T system and make it fit. I suspect it'll go right on, might need a reducer at the front end. If it does, modify the downpipe rather than the system and that ensures you can sell the exhaust on again.
I have to ask what you intend to gain though? There is literally NO point tuning a 1.8 NA. If you want a bit more noise, fit a backbox. If you want power, sell it and buy a turbo car.