I know this is a long shot but you never know - someone just might have these parts laying around.
M148651 seat bracket
M148647 seat bracket
I'm doing a conversion to a Michigan suspension seat on my 2520 following along with this thread.
I knew the price of these seat rails going in but find it so hard to pull the trigger at $47-$48 each. Just thought I would make a last ditch effort to locate this pair before I order from GFP.