The best advice I could offer is VeloCals, but their service has been known to be spotty (however not in my own experience with them; they were both friendly and promt) and to my knowledge they don't make LeMond decal sets (although I did suggest it to them back when I ordered some restoration decals for my Trek, and they liked the idea). So, who knows. Contact them and ask; the worst they can do is say no.
The only specific source for LeMond decals that I've seen is apparently in Nancy, France: there's someone out there who occasionally posts LeMond restoration decals on eBay. I believe there's some kind of UK connection here, like- you might have to order them through some UK bike shop or restorer or something. Any Forumites in Old Blighty have any further info?