From what I can tell in the pics, the frame is not in bad shape at all. If it was me. I'd sand off the rust, clean off the goop / sealer around the glass and cowl rubber (maybe replace) and refinish the frame. Unless there is alot of rust through damage that can't be seen in the pictures, especially on the bottom (windshield folded down), Don't waste your money on a new frame. You'd have to paint it anyway.
"We and the world will always be at war. Retreat is impossible. Arm yourselves for the conflict." Leif Enger