I've ordered the new motor from Xiongda. It was ordered on 21 April, dispatched immediately, and by the 30 April it was in Slough. Maybe it'll be delivered today, but I'm not in a big hurry for it, because the Panda wheel is working fine.
The advantage of this motor, is that I asked for it to be built for torque, rather than speed. I'm not often whizzing down a long tarmac road, I'm mostly bumping up a rough incline.
But today I suddenly realised that the motor would need to be built into a wheel. I have a suitable rim (when I bought the rim for my old motor, I bought a pair), but I'm spokeless (unless I reuse the spokes from the wheel that doesn't work, which I don't want to do, because I might be able to fix it. So I went back to my previous spoke supplier, Tiller Cycles, and ordered 36 13/14g Sapim Strong, 213 mm long, for £31. I want the "Strong" because I'm a bit tubby, and I ride over some very rough ground. They should arrive in a few days.
When all this arrives, I need to build the wheel. I could have it done professionally for about £25, but then I'd miss all the fun. The best reference for this (and for all things bicycle) is Sheldon Brown whose guidance I use every time.
The most difficult part is truing the wheel; the idea is that when it rotates, there's no wobble. Truing can take a long time, but once it's done, it shouldn't need future work.
There's also the matter of getting the tension right. You could spend hundreds of pounds on a tensiometer, but I do it by plucking the spoke and listening to the pitch. I'm aiming for D# above middle C. You can get other notes on youtube by searching for, for example, "C# for instrument tuning".