Not sure if I got it at Home Depot or Menards, but I got a bare fixture
with no shade called Homelux 48" striplight. It has rapid start ballast
and can use 40w, 34w or 25w 4' bulb.

I have not installed it yet because the old fixture boxed in over the
kitchen sink on an outside wall only occasionally gives me starting
trouble in extremely cold weather (maybe colder than room temperature).

If it's having trouble starting you may just have a bad ground to the
fixture.

Those strips are easy to find, though they have those horrid low power
factor ballasts that run even the 4' 40W tubes at no more than about 25W.
You can get *far* better performance by fitting one with an electronic
ballast and F32T8 tube.