Regarding a corrupted Memory Stick, you may be able to recover the data using the free Sony Memory Stick Data Rescue Service
. This is a downloadable utility, just click on the link which I have provided for you.
Your camera is designed to take Sony Memory Stick Pro up to and including 1GB capacity. Larger capacity Memory Sticks do not work in your camera, but as you have found out for yourself the 1GB versions are no longer manufactured. Your best option is to contact camera shops directly as there are bound to be some which are still in stock. You could also try sites like eBay and Amazon, but be very careful who you buy from as there are plenty of fakes with inferior performance.
You can use Memory Stick Pro or Pro-Duo provided the latter is supplied with the adapter which is normally included to make it the same physical size as a regular Pro. You can also find Memory Stick Micro (also known as M2) in the 1GB capacity which you require, but even with adapters it might not work with your camera due to other hardware issues.
1GB cards are generally regarded as obsolete, so many folks will have them lying unused due to upgrading. Why not try asking for one on your local FreeCycle or Freegle (UK only) group? You'll have most chances of success if you ask for the smaller 256MB or 512MB Memory Sticks, and they will also ensure maximum compatibility with your DSC-P73. Although it was designed for up to 1GB, such cards did not exist at the time so it was never officially tested with them in practice.
I hope that my posting has been of some assistance to you and helps you to obtain what you require. All I ask in return is that you take a moment to rate my answer.