What are rainbow lilies? Are they true lilies (genus Lilium)? I have never heard of them.
Now Lilium 'Starlette', I have not seen that on the market in a long time. I have suspected it is the same as Lilium 'Forever Susan'. If it isn't the same it sure does look like the same and would be a good substitute. Just google around for a vendor, I am sure it is still on the market.
Is this what you are looking for? Scroll down for more photos:
Asiatic Lily (Lilium 'Forever Susan')