I noticed Logitech is finally making a new Playgear case for the PSP slim and it seems as though they are also making one for the DS Lite. It doesn't look as good to me as the PSP playgear but I really like that case so I may have to give this a shot as well. I hope it isn't too bulky. Both are due out in August.
http://www.logitech.com/index.cfm/gaming/portable/nintendo_ds/devices/4568&cl=us,en
http://www.logitech.com/index.cfm/gaming/portable/nintendo_ds/devices/4568&cl=us,en