Are you looking for a whole wheel to take apart and build your motor wheel with, or just a rim and spokes for the motor? (noting that you'll probably need different length spokes than come with a regular bicycle wheel to lace the motor into it)
Assuming you don't need a whole wheel:
For the rim itself, it partly depends on the load the wheel has to support. If it's typical bicycle-duty, a typical double-wall aluminum / alloy bicycle rim will work. If it's higher weight or harsher riding conditions, a stiffer heavy-duty rim might be better. I'd go with eyeletted nipple holes, as they help minimize the chances of cracking at the holes, partly by helping spread the force of the nipples more evenly around the hole, etc.
For spokes, Sapim 14-15 butted or 13-14 butted would work well for most typical wheels, along with matching nipples for the nipple hole size of the rim.
More specific good info on both of those can be found in many of Chalo's posts on this general topic, among other members that have built lots of wheels (PapaSteve, etc).