Mate just leave it as is looks smart as without the stripes I really dont like the stripes I find they look cheap and tacky tbh mate, nice looking GP this love the colour!
You could try a fiat dealer and ask them. I know fiat do a range of decals and stripes and I think fitting is included in the price (not sure tho). Check the fiat website and look under accessories and they got penty there. OR you could try ebay or some 3rd party place.