I ordered a nice sturdy fork online last week. I asked for recommendations of forks from the Tidalforce group on Google. They knew this was a front hub motor setup so they recommended the Surly Instigator solid steel fork. It's designed to replace 100mm travel suspension forks so it's extra tall. It's also very wide so that it can handle 2.7" wide tires! I ordered it from here:
The price of $63.24 was the lowest I could find by about $16! Shipping brought it up to $71. I'm expecting it to be delivered today.
It's a very solid, straight tubed steel fork with strong looking dropouts. There are removable cantilever posts and also a disk brake mount.