someone else asked the same question .. roll out the same answer ..
Planet bike is another battery light which has a blinking mode , there is a bracket that works with the Euro rack holes ,
its still not permanent .
Rack Blinky 5
a USB charged version
Superflash USB
NB: not all mounts sold with all models .. So you might have to order the other kind of mount..too ..
BUT from Riga , Latvia , the distributor to your shops would unlikely be out of Madison Wisconsin usa,
UK seems to go to the same Taiwan Manufacturer ... and distributes it under a different name.
I have that Tubus rack , but used a B&M 4D Toplight Senso. the AA batteries run it ,
the only mode for flashing is when in senso mode in daylight , you enter a tunnel.
then it comes on and does a safetey flash , but back in the sunlight again the sensor turns it off .