I have MANY (too many) solar garden lights. I got 10 for free as a promotion to save electricity from my electrical utility company and they are more than 15 years old. The Chinese Ni-Cad AA batteries lasted less than one summer so I replaced them with name-brand Ni-MH cells. The wires on the yellow LEDs rusted away in one year so I replaced them with different colored good LEDs. The plastic solar panels got sunburned so I polished them then coated a clear finish on them.
I bought 10 for $1.00 Canadian each (($.70 American) from Walmart and only one worked brightly all night following a sunny day. I returned 9 and replaced them and found another good one. I returned some again over and over (the clerk said, "You again?"), sometimes keeping a good battery from one and installing it in one with a good sensitivity solar panel. They came with AAA Ni-MH batteries marked 300mAh and 600mAh with no manufacturer's name. Most measured only 100mAh, the good ones I kept measure about 500mAh each and the ones marked 600mAh measured less than 100mAh. I added a Schottky diode and capacitor and replaced their white LEDs with multi-colored flashing/fading LEDs. I measured the forward voltages of all the surplus white LEDs I got and picked two that were the same and connected them in parallel in one solar garden light.
A few of my solar garden lights had transistors and a LDR that rusted away in one year but most use the solar panel as a light sensor and charger to feed the Black Blob On Board.
Very bright solar garden lights are sold and are fairly expensive. I would not find their parts anywhere to make one myself.