Greg Softley (Cyclomondo on Ebay) will replicate any decal set. Send him the highest quality pics you can with a ruler included in each shot. He compensates for frame curvature when he replicates. Better yet, if you ar going to respray, then you can cut the old decals off carefully with a razor blade and flat scan them. (You have to cut the paint off too.)
His price will vary depending on the detail involved and the resale value. If you are giving him a pattern that he can sell to lots of other people his price could be around $20 USD, but if it's not a common decal, then the cost will probably be between $40-$50 USD for the set I'd say.
I have a list of firms that do original and repro decals, but it's on my home computer, so I might put that list up tonight. I would suggest contacting those companies before resorting to getting replicas made.