1st choice is a dry-suit.
That maybe out of the question though
Farmer John is the best best bet for paddling. Try to avoid wetsuits that restrict arm movements. 3mm should be the thickest, any more than that and you will cook while out of the water.
In fair weather this should be sufficient.
If it is raining or a chilly wind a paddling top in addition to the wetsuit might be an option.
http://www.mec.ca/Products/product_deta ... 1884631622
If you don't want to drop the cash, some polypro long underwear top and bottom, will warm significantly and cut the breeze.