Amanda of BloggerBuster has a recent comment widget generator which I tested at Safety Tips and Tricks.
What I did was copy-pasted the blog URL (actually you can put any URL, it will make no difference) and pasted into the box for the blog URL and just left all the other variables at the default. It is best you do that in a browser where you are logged into your Blogger account which has the blog you want the recent comments widget. Click APPLY, then GENERATE and another tab or window will be open where you will need to select the blog again from a list of your blogs.
Result: It works, but once the widget is added to your LAYOUT, you will not be able to drag and drop (move) initially but was able to finally move it to the bottom of the left sidebar of Safety Tips and Tricks. You can test it - try leaving a comment there.