Our brothers across the pond seemed to take more interest in the 80 than we did magazine wise so try this most excellent site which has all the copies I know of, of Sync magazine.
Most of the early volumes are dedicated quite well to the 80 and have some interesting type-ins.
As for the stock market program I wouldn't be surprised if you find it there.
Again welcome aboard and don't hesitate to ask questions as there are some very clever bods here and do join in if a topic takes your fancy. There is also a welcome area on the home page where you might want to introduce yourself.
After some searching I found this, taken from here...
http://www.stefanopaganini.com/2017/04/ ... -magazine/
Is this what you are looking for?
I actually had already spotted this program myself on the same website (it took me a little longer than you to find it!) I will give that program a go at some point as it looks very similar. I initially thought that my friend may have copied a type in, but now think he may have wrote the program himself? I remember he had his ZX80 set up in his garage & I was amazed so see a small B&W TV running a simulation of several stocks fluctuating in price over a time stamp. Sounds silly nowadays but at the time the most advanced TV game was pong! This began my interest in computers & as with a lot of people went out & purchased a ZX81 that I still own.
I have read that thousands of programs were written for the ZX80 so was a little surprised to find so little online. I love these early machines in a time when people thought anyone who owed a computer was a geek! How the times have changed with computers now everywhere.