No, I cannot give you a prescription for lithium.
Because lithium is used to treat bipolar disorder and you do not have bipolar disorder. I understand that your naturopath tested your hair for trace elements and his tests show that you have low levels of lithium; however, you just said you didn't have any health complaints.
You want to try 5 mg of lithium per day, but the smallest tablets I can find are 100 mg. Are you really going to cut this tablet into 20 pieces? Even if you did, if anything happens to you, like thyrotoxicosis leading to hypothyroidism (a side effect of lithium)... how am I going to explain that I gave a perfectly healthy patient, who was not bipolar, a prescription for lithium?