My information is that they discontinued and closed out the RS 44-610 switch about 2 years ago (IIRC). I picked up a couple for different uses for US$2 each at that time, and they work with the RH Designs Stop Clock Pro and (with a 3/32 to 1/8 adapter) the Gralab 450 and similar timers. You might find the occasional stray, but RS does periodically gather discontinued items from stores and send them to regional closeout centers, so at this point they may be very hard to find in stores. I used to visit a RS closeout store in an industrial park in Woodland, CA for this kind of stuff.
Lee