No, there isn't a way, and there never will be a way to connect any DS older than the DSi to a WPA2, or even WPA connection. Furthermore, there also will never be a way to play old games that don't have DSi support on a WPA2 or WPA connection.
There are a few ways you can connect online:
- Change your modem's/router's settings to WEP
- Get a second router, connect it via ethernet to your main one and leave it unlocked or with WEP security as a dedicated access point for your NDS
- Use a mobile phone to create a hotspot
- other similar methods, all involving different ways of making an access point
Alternatively, just look for any public networks you can use.