How do I comfort a Christian trying to convert me that I'm fine as I am?

You do not need to comfort them. Just change the subject and if that doesn't work then violently throw your beliefs at them as they do to you and when they get annoyed just say that you are their mirror.

I simply state I am not interested in what they are selling, desire what they promise and are quite happy in my life and wish that some day they will find the same.

Murder him and he will never try again-.-

GOOD LUCK WITH THAT ON JUDGEMENT DAY

You couldn't comfort a Christian with those words if they knew you were not yet saved and didn't know Christ, because you are not fine. You are unsaved and on your way to hell, on the broad road to destruction and still in the Devil's kingdom of darkness.

If you get born again through Christ, then you can enter God's Kingdom (John 3:3-5) and God will deliver you OUT OF Satan's kingdom of darkness and translate you INTO the kingdom of the Son of His love (Colossians 1:13) and remove you off the broad road to destruction and put on the narrow, difficult road to life (Matthew 7:14 & 14)

If you believed in Jesus Christ and got baptized ("He who believes and is baptized shall be saved" (Mark 16:16) then God would crucify your old man - (your old adamic sinful nature) in baptism and you would no longer be a slave of sin (Romans 6:6).

Then you would be fine but not before conversion. You need the Saviour just as much as all the rest of us because we are all born sinners.

Say "Thank you for caring about me, but I'm happy where I am."

He should then leave you alone

But you won't feel fine when God judges you to eternal hell. You will wish forever that you'd never been born. Its a loving warning - and Gods promise - not an idle threat.

Mar 6:11 Whosoever shall not receive you, nor hear you, when ye depart thence, shake off the dust under your feet for a testimony against them. Verily I say unto you, It shall be more tolerable for Sodom and Gomorrha in the day of judgment, than for these.

Mat 13:42 And when he shall cast the wicked into a furnace of fire, there shall be wailing and gnashing of teeth.

I have religious friends and I just tell them that many stories in the bible are scientifically and physically impossible. All they can say is "god can do anything". I say "prove it". They can't.

You own a proposition and it is not for sale. '' Would you like to go shopping''? etc etc.

Atheist.