My favourite sources for decals are:
squadron.com,
meteorprod.com,
flightdecs.ca,
airconnection.on.ca and
greatmodels.com. All of these places have large databases of decals, especially Flightdecs. If you can't find them at these sites, then they probably don't exist.
BTW, is this the Italeri kit? And if so, have you tried writing Italeri for a replacement set? i've found them to be very good about replacements in the past. Might be worth a shot.