I've been using MH Tempest SL gloves that have a Conduit shell, reinforced palm and micro fleece liner. They are like rain shells for your hands and perfect for hiking in cold rain with poles. Of course they don't make them anymore, but they do have an Epic shell version. About 4oz.
Mitten shells do seem to be a great MYOG project--- trace your hand, sew around the perimeter, seam seal, and turn it inside-out. Ugly, but light.
I saw a guy riding a bike in downtown traffic in the rain one day, with bright yellow dishwashing gloves. Cheap and easy to come by! Playtex makes some disposable ones that are $4.5/30 --- not a fan of "disposable," except they must be lighter.
IMHO, Sealskinz are the best for really cold/wet wear. http://www.sealskinz.com/cgi-bin/psProdDet.cgi/KJ751||~@c~@b|0|user|1,0,0,1|53|
Found them on sale in the US at http://www.greatoutdoorsdepot.com/seal-skinz-gloves.html I haven't dealt with this vendor --- got mine in a thrift store for $3 :)