Disclosure - DO AT YOUR OWN RISK!
I'm thinking maybe two lengths of angle iron (represented by "A" and "B" in the image) that just fit on the inside of the open end of the A-arm and placed around the fulcrum pin (BTW, that may be a British term). Perhaps a few hose clamps, muffler clamps etc. to hold the halves together. This way the angle iron transfers any residual pressing force to the other side of the A-Arm and helps to keep it from collapsing but there is room for the second bushing to freely move downward. Just keep an eye on the clamps because with the forces involved the angle iron might fly free! You might want to paint AFTER doing this because I'm sure there will be scratches.
Oh, and please excuse my less than stellar drawing skills.