This was a topic I raised about a month ago and there was a suggestion of an item from the Axminster catalogue.
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was ordering from Axminster anyway so it was easy enought to add this in. I was a bit thrown when it arrived as it's a 150mm length of6mm threaded rod with a knurled nut with a groove machined in it. It's taken me a month to find out that it is a very basic but simple solution to the problem - part of that month was finding quite where I had put the side fence ! OK senior moment.
I've got one of the B&Q 1200W router's and it has, presumably like the m/c this device is designed for, a 6mm threaded hole in the base plate. Threaded rod goes into this hole - the side fence has slot in it which fits into the groove in the knurled nut and hey presto. It's not as nifty as the fancy ones but for £6 it'll do. There's no calibration but the thread is M6 x 1 so some marks can be added to the nut so that one turn is 1mm, etc.
Rob