Sorry, that was probably my fault for putting the photo up. I had to use that style draw bar because the original draw bar mount is not the original. It is one that was adapted from a Kubota before I bought the tractor, and it is not strong enough now to tow, and I don't have the draw bar. That is a nice Iseki, and it looks like you are making headway with it. What part are you welding? I actually have really not had an issue with using the lift arm draw bar when towing the trailer. I usually have a load of wood, or hay in it, and I have not had an issue. Once it raised up in the air, however that was when I had about 400 lbs of grain, and multiple bags of shavings as well, and I hit a bump, and it went up, but it went right back down. I had to attach that draw bar A frame that connects to the toplink to keep the draw bar from rotating in the lift arms. It has worked great. You may want to consider this option, and then if you have issues, attach a chain. I know that lens12 said that he can get the original draw bar mount, however I am not sure how much it will be. The lift arm draw bar has worked great for me, and I have even used it to tow trees out of the woods. The only part I had to remove was the black piece where the ball is attached in the photo, because it bent when I was towing a trailer of logs the other day. It must have been pretty heavy, because that part was rated for much more than I was towing. I just put the ball in one of the holes. See the attached photo. I think that this may be your best bet. You can pick up a draw bar at tractor supply, or online for about $20-$25. At that price you really can't go wrong. The only part that was more expensive was the A frame portion, however the only reason I went with this style is because I have the fast hitch attachments on the end of my lift arms, and the normal draw bar stabilizer, see link:
Drawbar Lock, Cat. 1 - 1000786 | Tractor Supply Company would not fit, however it should on yours.
Cross Drawbar, Category 1, 3/4 in. dia. - 0288975 | Tractor Supply Company
The bungee cord came with the fast hitch, and they keep my lift arms in tight when I have a larger implement on the back like the dirt scoop.