It has been mentioned several times that we could have our cake and
eat it too if := was visually converted to the left arrow by something
like shout, but preserved in the source file. Has anybody done
anything like this yet? 

(Or any other solution which gives a visual left arrow for those of us
who are attached to it, but preserves := in source files)

The reason for this question is that I need to use a non-patched font
and I am attached to the left arrow :)

Michal