I was going to suggest 4 foot shop lights (T8 or T5), but if they won't fit, yikes.
You might take a tape measure to HD or Menards. If they have some fixtures on display, you can measure length-overall and try to find one that's shorter than most ... but the tubes take up most of the fixture and finding one as short as 47" may not be possible.
That is a tough one.
My HD had a big display of many lighting fixtures including floodlights. They might be inefficient, but you can find something with lots of lumens and not too many bucks. Just make sure that replacement bulbs aren't more expensive than the fixture, if you get something unusual!
One fall back is just plain screw-in (mogul base) CFL bulbs, with as many lumens (or Watts) as you can afford. If the CFL bulb is a "floodlight" type, it has a built-in reflector that will aim the light into a cone. But those often have some diffuser over the bulb, which reduces lumens. If you have a pole fixture that accepts screw-in CFLs, the pole probably has built-in reflectors that throw SOME of the light forward.
It would not be TOO hard to construct four boards with 2-4 screw-in bases, wired to 120 VAC. Then you could mount each board to aim at one shelf. It might be hard to adjust.
This isn't a very good answer, but it's all I can think of. I think that 3 foot shop olights are rare, and bulbs would probably be more expensive.
LED lights are still expensive, and some cheaper Chinese ones just burn out very quickly due to unbalanced power going to each LED.
