I don't know anything specific about your calculator, but I'm betting it can be fixed.
First thing I'd suggest is removing the LCD display in order to get that ribbon cable that stretches over the solar panel out of the way. It would be safest to remove the motherboard, but it's obviously not made to be removed; it looks like it's held on with a single Phillips screw and five plastic welds.
At any rate, once the LCD ribbon cable is out of the way, you'll have to take either a soldering iron or an X-Acto knife and either melt or cut off the melted plastic holding the solar panel in place. Next step is to either unsolder (preferred) or cut the black and red wires going to the panel so it can be removed.
Next problem is to find a replacement. I wouldn't count on finding parts for your specific calculator, although it's not impossible. You should measure the outside dimensions of the panel and do a search for a generic replacement, perhaps something similar to this one, for example.
30x4mm 3.3v 2ua Dim Light Thin Film Amorphous Silicon Solar Cell Ito Glass For Indoor Product,calculator,toy,0-3v Battery - Alternative Energy Generators - AliExpress
Unfortunately, I don't know enough to tell you what voltage output you'll need from the replacement panel; solar technology has come a long way since your calculator was made.
Anyway, once you've found a replacement, you should temporarily hook it up and verify it powers the calculator. If it's all good, then you'll need to remount the panel into the calculator; you can probably resecure it well enough with hot glue. Reinstall the LCD panel and put the rear cover back on and you should be all set!
With any luck it should be a straightforward repair; the hardest part I imagine will be locating a replacement part. I'll be happy to help look for one once we know what size you need; most of the ones will be measured in millimeters, but it's easy enough to convert if you only have a US Standard ruler.
I'm also hoping some of our more knowledgable contributors such as @oldturkey03 and others might have some thoughts on what voltage output to look for; I assume we won't be able to find out from measuring your existing one since it's broken.
Good luck; let us know how it goes and what you find!
what is the specific model? does it still turn on?