I think you'd have to do records for yourself. highly unlikely you'll be able to find that sort of info. Keep a little black book on it
or even a diary/mobile phone, whatever electronic gizmo you may have to make notes in, take it with you when you go to the store/s, jot it down.
There was a website here that listed prices in major supermarkets day-by-day, but the individual locations would use it to undercut their competitors once the prices were listed. It didn't last long.
Prices vary greatly here too. Sure, there is the issue of what is in season, but I went to the store tyesterday and today. Yesterday - watermelon 77c/kg. Today - $1.42/kg. Avocado - Yesterday $2.75 each, today - $1.43. I really couldn't see the difference in the fruits, and I'll bet you they are the same pieces that were there yesterday. Oh, and lamb chops!! They do one week a month where it is selling for $7.99/kg, then for the rest of the month it is $11.99/kg. I wait for the cheap week. Then freeze a stack.
A lot of it depends on which day of the week is pay day generally in a given area. Prices skyrocket that day. Typically here it is Thursday. I try to avoid the stores on that day