I recently had to do this and the Ross people offered a solution.. below is that solution..
This Timer Code gets rid of the leading zero's for hours (00:59:00), minutes (09:59) & seconds (00:59).
If you right click on your text object (that has the clock widget) you will see an option for "edit script events". (sometimes the text box loses focus and selects another object in your scene, if that happens lock the object it keeps selecting, then recheck on the text box and it keeps its focus.) Within 'edit script events', select 'OnSetText'. If you don't see 'OnSetText' then your focus isn't on the Text Box.
Type the below code on the right window:
if left(text,5) = "00:00" then
text = right(text, len(text)-5)
end if
if left(text,4) = "00:0" then
text = right(text, len(text)-4)
end if
if left(text,3) = "00:" then
text = right(text, len(text)-3)
end if
At the top of the window there is a button that looks like a lightning bolt. This will compile your script, this must be done in order for it to function.
Start your timer, load the framebuffer and watch the "magic" happen.