I have an older fridge with the single lamp on top. What would be a better lighting alternative? Without using LED, Would installing small incandescents, or xenon along the sides give the fridge more even lighting? Has anyone done something like this, or better?

There are a tons of problems with hacking anything inside the fridges, mainly electrical (make it robust against humidity, to not be easily kicked out when manipulating with things in the fridge, making sure the water won't leak through the added mounting holes where it does not belong and e.g. compromise the thermal insulation or damage other things, no wires would get rubbed off by the compressor vibrating with the whole fridge,...). So I would personally keep it original. And remember it for the next time you will be shopping for a new fridge (once the old dies,...) and add it to the requirement list you have for the new one.