UKH

I've got an old Jetboil Sol that is in fine working order, but the pot has rusted after my partner put it back in storage still wet. As the Sol has been discontinued, does anyone know which current models of pots are compatible with it?

Any of the PCS, Sumo or Flash  pots will fit the same mounting (I use them interchangeably).

Genuine question what is it made from that rusts?

Only one material that rusts through so as to be unusable...

If you use the word "rust" in the every day English use as "corrosion" (rather than the technical use for oxidative corrosion of iron, steel) then there are several possibilities.

I've made the mistake of putting some things in the storage box at end of garden when tidying up, supposedly for a week while juggling stuff about and found it again a few years later, to discover some alloys have "rusted" badly. Lost my Markill Stormy that way. Some bits were totally unaffected but the bit that holds the burner into the bottom was rotted where it touched the aluminium body. Maybe some galvanic difference, no idea, but it was ruined

That would definitely be 'corroded ' then 😝  Rust is very much ferrous metals only (inc. Stainless, but generally its significantly less substantial).

On a slightly less pedantic point, perhaps the OP can describe the damage or send a pic?  Surface rust or corrosion, even relatively deep, can be easily be removed (from steel/stainless/aluminium and even titanium) but holes are of course terminal.  Would be surprised if something stainless or aluminum had corroded so much as to be unrecoverable, unless it was at a ally/steel or ally/brass contact point (galvanic).