Endless Sphere would be the best place to look for ideas, here's the non-hub motor forum.
https://endless-sphere.com/forums/viewforum.php?f=28 The most popular ones now are the BBS02, BBSHD, and Cyclone 3000 (from least to most powerful, both stock and potential). Any of them should get you to 50km/h, just depends on how fast you want to get there.
Not sure how much power you'll use compared to a bike, but you'll probably be looking at a 48v 15Ah pack for one way or 20-25Ah for the whole trip without charging (again, I'm not sure how much of a savings the velomobile will give over a bike, so less might do the job). You'll want some sort of lithium battery, lead acid isn't worth all the drawbacks.