Damn Small SQLi Scanner (DSSS) has been made as a PoC where I wanted to show that commercial (SQLi) scanners can be beaten under 100 lines of code.
It supports GET and POST parameters, blind/error SQLi tests and advanced comparison of different response attributes to distinguish blind responses. If you are satisfied with your commercial tool scanning results then I believe that you could even be more satisfied with this one.
As of optional settings it supports HTTP proxy together with HTTP header values "User-Agent", "Referer" and "Cookie".