Jacobsdaddy06,
It appaears the reason that piece wound up breaking is the two 'straight beams' got bent(most likely from getting a rock in the sickle),,and started beating themselves up.
All you need to do is two things to make a nice solid repair.
You will simply need a stick welder,,AKA,buzzbox.And some Lincoln Ferroweld welding sticks.(About $8 per one lb box.) 1 box will probably do this job for you.
1) Measure what the length SHOULD be of each of the straight beams.Allow an extra 1" to overlap your new cut beames to the existing broken beam part.Decide were you want to cut each of your two beams(shown),,to the same length
2) Cut you two pieces of steel stock,,slightly heavier than what the current beams are.
3) drill the holes for the bolt to go through at the reciprocating end of your newly cut beames.
4) GO to any tractor supply place that sells Lincoln brand rods and get the "Ferroweld" It will be on the label as used for 'dirty welded cast ioin",,FYI
5) Cut off the existing/broken beames in the same spot.
6) Set you buzzbox welder to 100 amps
7) Overlap your new beames to the exisint beams and simply c-clamp each
8) Go to town welding the new beames to the exisng/clamped beam.
9) Done
Take Care,
BC