Sorry you didn't get a reply, as you can see this form is pretty dead.
If you're still interested, I'm of the opinion that if it wasn't designed and built from scratch, then almost everything on the original, whatever it was, was replaced. As you probably know by now, you can use almost anything for a tensioner. To get to the point you can print something, you can rig something up with zip ties. Although my comments are likely moot by now.
I did want to warn you of a subtle problem with the printer that can be hard to identify. Looking at the pic isn't enough to be positive; but I think the frame will exhibit twisting and needs to be reinforced against that. I'm referring to the top twisting left and right with respect to the bottom.
Hope you already got it working.
