I'm sorry, I'm not trying to cause trouble, but I have never understood putting a scope on a revolver and a Colt Frontier Scout seems like a particularly hard to understand situation.
The single action lockwork is not precise enough for quality target shooting so scoping this gun seems useless. If your friend really wants a scoped .22 pistol I would suggest a Browning Buckmark or some other target pistol that comes with a rail or mounts. A single action Colt with optics sounds horrid, to me.
JMHO