Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother, we are appreciating your commitment to your religion and its rules, which is the duty of each Muslim.
In fact, you may go to hair transplant operation. Tattoos are not allowed; you should avoid it.
Responding to your question, Sheikh Kifah Mustapha, the Imam and Associate Director at the Mosque Foundation, one of the largest Islamic Centers in Chicago, states:
Growing hair is not an extreme necessity in Islam and for that nothing of haram can be bend to accommodate it. Islam, through the Sunnah of the Prophet (peace and blessings be upon him), prohibited tattoos; he said: “Allah Almighty cursed those who make tattoos and those who ask for it.” (Al-Bukhari)
And because of that clear text, I see no space to use tattoos for such reason but going to medical treatment for hair implants is permissible.
Allah Almighty knows best.