is l-dopa and a dopamine agonist the best option.

Tyrosine on its own although safe doesn't boost the dopamine levels very much.
L-dopa although dangerous in the long term does get your dopamine levels back up until later when you also need an agonist.
However their might be some treatment though not overly effective in the short term in the line term might help the brain redevelop the substantial nigra.
Here some thing that might help
Artichoke may aid the biosythensis in the gut
Acetyltyrosine might actually be able better to be better synthesised into dopamine than tyrosine.
A small amount say 1mg a day of forskolin might help cellular regeneration in the brain.
Alpha GPC should enable higher Acetylcholine levels in the brain especially over the long term
Pithy citrus fruit juices should help the blood processing
Arachidonic acid might help the regulation of hormones in the brain
L carnitine might help protect the new neural development
Omega 3 high dha and spa oil might help healthy brain growth
And d and l Serine might help aid nervous system development
Silver needle white tea may make the process more youthal and get the dopamine receptors Woking in a way which helps not hinders repair.
Put all this together with a healthy varied diet excluding foods which can disturb your dopamine levels like dairy or chocolate and after a year you might be better off than a person who soly relied on pharmaceuticals.
What is your experience.

Argmatine might also be useful in preventing further damage.

I rely on tyrosine personally. I don't have Parkinson's. So can't draw any personal conclusions about the protective or preventative aspects. I like tyrosine because it helps the body balance itself. N-acetyl-tyrosine didn't have anything like the same effect for me.