In the UK197, the reset pin (#4) is tied to the trigger, thus on retriggering the UK197, the whole device is reset, which probably accounts for the glitch you see. I have not tested any of the retriggerable circuits presented above.
Since the "boss" wants an off the shelf answer, you may have to find another monostable controller (i.e., a retriggerable one) or do a little re-wiring of the UK197.
Have I understood your question correctly, and is the momentary glitch really a problem?