What is the best way to connect to eBay while out shopping?

I want to be able to look up items on eBay while i’m out junk/antique shopping. what would be the quickest and least expensive way, as far as monthly charges; a laptop computer or some type of phone – blackberry – etc? i have a computer at home and a cell phone, but know nothing about laptops, blackberrys, and don’t even know what a PDA is. i don’t mind investing in the hardware, but want to watch the monthly charges. thanks much in advance!