Some driveshafts are indeed made in one piece and they are expensive to replace unless you do a workaround.
The driveshaft in my Merkur was made like this and the driveshaft was only available through the dealer at 700 bucks plus; and that was 10 years ago.
I modified it to use Subaru U-joints. Total cost about 40 bucks. If you don’t do your own repair work it will cost more.
Check the Yellow Pages under the “driveline” category and pay a visit to their shop if you have one in your area. They may be able to get around this problem for a few hundred dollars. It’s worth a shot anyway.