This version of the belt tensioner has been working in the printer for months without any issues so far. It requires both screws to be tightened the same amount to make sure the idler is straight and stable.
Printed in ABS. It might work if printed in PLA as well (I have not tested). I printed with the 4 legs in horizontal direction to ensure strength.
This should fit the original frame without any modifications. I have lowered the bearing position by a bit to make it line up with the belt holder a bit better than the original part. I have also made small bumps around the hole to make sure the nut and bolt could be tightened a bit more without hindering the bearing.