I think it is way too expensive to be a simple piece of plastic. Plus, i should pay 18 dollars for delivery... for me it is a not. Unless someone here in Europe with a 3d printer wants to print it and sell it for a more reasonable price (i think, nothing more than 10 euro).
I have finally used the Chinese pad I bought in aliexpress. I added some water and floor detergent (3 caps each 40 ml with a small amount of detergent the rest water). The result is pretty good. The robot did the usual aspiration but left a regular pattern wet floor behind. One wet pad was enough to clear one average room and maybeven it could do something more. It does not scratch the surface so if there are dried marks they will be still there. But the floor in the end was so clean I had never seen it. It also had that good smell it has when you mop the floor. The satisfaction of watching a robot doing my job was more than the actual saving of time... I tried to record a video but the wet spots were not so visible as I could see them only with my own eyes. Anyway it works. I have tried it 4 times and the unit does not seem damaged. The very first time I used maybe too much water and that messed with the wheels sliding over the surface too wet and the unit looked "lost" some times. But when I put the right amount of water it was OK. I found that amount to be about 100/120 ml of water/detergent. I advice to put about 1/10 detergent and the rest water otherwise if you put more detergent the floor can be sticky.