Even if they did, the P40 was discontinued because it was prone to user-induced malfunctions occurring under recoil. Basically, anything less than a death grip had a tendency to cause the same sort of malfunction that limp-wristing can cause among certain pistols, so Kel-Tec discontinued the P40 because they were constantly getting perfectly reliable P40s sent in for repair and although they supposedly attempted to remedy the issue by altering the user manual with instructions on how to grip the P40 firmly/securely, it didn't work.
Unfortunately, the P40 was essentially defective by design, an extremely lightweight .40cal pistol with a tendency to malfunction under recoil.
So even if you could track down both a used P40 and a .357 SIG conversion barrel for it, you'd then have to contend with the extremely narrow margin for error while shooting it, and that's really not something you want out of a carry pistol.
Unfortunately, the P40 was essentially defective by design, an extremely lightweight .40cal pistol with a tendency to malfunction under recoil.
So even if you could track down both a used P40 and a .357 SIG conversion barrel for it, you'd then have to contend with the extremely narrow margin for error while shooting it, and that's really not something you want out of a carry pistol.
