This is not a "minimal pair", however cinquante (IPA: \sɛ̃.kɑ̃t\) contains both sounds. I heard records of people pronouncing it, but the difference is so subtle that to my ears it's all the same.
Please record yourself while you pronounce slowly some words containing both sounds. SLOWLY, please, and if you could repeat each word twice I would really appreciate it.
Thank you!
cinquante
but please read notes
cinquante, enfant, plante
bienvenue, bientôt,
bain, vin, plein, pleine