Hello Piemuncher and welcome.
That is indeed a very sad 750 twin and is quite short of a little TLC, well maybe a lot ha ha.
After saying that it is a doable project but you would have to be in it for the long ride. It looks to me like a 1976-1977 B1 or B2 model. You will have to decide which path you want to take. I would personally would want to restore her to her original glory but that will take a lot of time and money but above all commitment. Most of the parts would need replacing. You are right that parts aren’t as readily available as other models but they are out there. Many can be sourced on ebay which I have been doing for the last 20 years or so and I now have quite a large stock of both new and used parts. I have also sourced many new parts.
I would happily have her given to me but you now have one of the biggest decisions of your life to make.