Maybe double check the name. Viola Katherine doesn't appear to be a registered hybrid. Which might be why you can't find it. It's possible a local grower just named their own cross and didn't register, so then it will be quite difficult to find.
scobo -
You should probably ask one of the administrators to help you change your username to something that is not your email. Not good for internet security reasons.
Epicattleya Voila when it was registered in 1966, it is officially Guaricyclia Voila now (Guarianthe bowringiana x Encyclia cordigera).
Note: It is Voila, not Viola.
You may find more information with the correct spelling of Voila, or with Guaricyclia instead of Epicattleya. It is an old cross though, so finding a source now may be a challenge.
As PaphMadMan says, the genus has changed, though I also ran across it as Catyclia online; it appears to still be available from a couple European vendors, and if I'm interpreting the listing correctly, the Missouri Botanical Gardens has one in their collection--you might try zipping them a note to see if they're willing to strike a division for you. Good luck.
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