Actually, you can buy most suppliers.
If I had to prepare them anyway, I would either use sodium metal or sodium hydride (NaH) into methanol, ethanol and isopropanol solutions.
But, be very careful. These reactions are exothermic and produce H
2 gas which can catch fire. Then your entire solution would be in fire... Add the reactant very slowly and cool the solution using a water/ice bath.
Once done, evaporate the unreacted solvent to dryness and there you are.