Do fluorescent fixtures rated for "Through Wiring" exist?
There should be a stamp/label on the fixture similar to 


  MAXIMUM OF 8 NO 12 AWG THROUGH BRANCH CIRCUIT CONDUCTORS SUITABLE FOR AT LEAST 90&deg;C PERMITTED IN BOX (4 IN 4 OUT).


Not sure that would be listed anywhere if you're shopping online, as most websites aren't great at describing products. Surely if you went to a physical store, you could inspect the fixture for the marking. You might also be able to find this information on the manufacturer's website, in their catalog, or by contacting them directly.