Panniers for Vado SL2 5.0?

Just got my first ebike, Vado SL2 5.0. Love it so far. I want to add a pannier for commuting to work (almost always in nice weather, only a few miles). I tried one from REI, but the mounting system didn't work on the Vado SL2. Any suggestions about brands that have worked on this bike? (I'd prefer a more briefcase/backpack style, rather than a roll-top.) Thanks.