Unfortunately, Online services for the DS/Wii are no longer being held up by Nintendo, meaning that trading online in B/W is pretty much impossible, so you'd either need to trade with a local friend who has B/W/B2/W2 and a system they can play one of those games on or you'd need a secondary DS and game of B/W/B2/W2. So sadly, there's nothing anyone on this site can do to help, unless they know you in real life.
On the bright side though, a 3DS is backwards compatible, so if you have a DS since the time where that was the latest handheld as well as a 3DS, you can use those consoles to trade with eachother. And you could use a copy of Black 2 or White 2 to trade between your version of Black or White.