a good new paper dictionary will cost you around $40. an awesome used electronic dictionary is only $70, and it has so many features! (although allot of them are useless to english speakers) but anyways, being able to just type words is so much easier than looking them up in a book. I would highly highly highly recommend you by a used electronic dictionary instead.
I think you would do better with an electronic dictionary.
as for where to buy, check ebay, facebook market, and craig's list. If your ballin rich you could buy a brand new one. they are around $200 I think. I googled it and came up with this. http://www.ectaco.ca/products/ectaco-partner-ek500/