...But what I think you are really asking for is something like an Ovation guitar--high quality, great sound, plastic back, wood front--and likely thinner than a "traditional" ukulele. Maybe someone will come out with that!
With regards to the wooden top and neck with plastic back, in addition to what has already been mentioned there are also:
1. Ovation has made some ukes like this under the name 'Applause' in both soprano and tenor scales, but most of the reviews I read were just meh, and replacing the battery for the built-in pre-amps for the electric models was an exercise in insanity - fellow UU brother Ian Chadwick has a good review on his site that sums it all up:
http://www.vintageukemusic.com/ukuleles/applause.htm
2. There this Alic soprano that seems to be available only in the UK from sources like Southern Ukulele Store and Omega Music, and brother BazMaz did a review here:
http://www.gotaukulele.com/2015/02/alic-soprano-ukulele-review.html
3. There are ALSO these Mahilele ukes, that come in 31 different colors and wood tops and patterns, sold my Mercantino Dell Ukulele in Italy which seems to be the storefront for Aquila retail and online direct sales:
http://www.mercatinodellukulele.it/...rtuemart&view=category&lang=en&language=en-GB
4. and of course there are Fluke and Flea ukes made by the
Magic Fluke Company for which there is an extensive thread here:
http://forum.ukuleleunderground.com/showthread.php?93637-The-Magic-Fluke-Company-Appreciation-thread
and that's all I got for wood top and some form of composite or plasic back/sides as of now...
I have several Fluke and Flea ukes, all play super comfortable, with great tone and near-perfect intonation, and are built for rugged use in the mainland USA, using local materials, run by a Mom & Pop family business company that runs all of their facilities on 100% solar power, and even feeds back excess to the power grid.
DISCLAIMER:
YES, I am a fan and repeat customer, and
NO, I am not a shill nor otherwise compensated for evangelizing what I think is I great product made by great people. I have paid for my MFC ukes with my own hard-earned money every single time.
So many ukes to try, and so little time (or money) Good luck.