Could someone paint my stainless steel flask?

You may want to consider something like this?

Plasti Dip Spray On Coating

Coat anything with a flexible rubber coating.

•Flexible - won't crack, chip or become brittle
•Insulates from electrical shock, vibration, heat and deadens sound.
•Provides safe, non-slip comfort and control.
•Durable - resists weather, chemicals, impact and abrasion.
•Available in red, yellow, black, blue, white and clear.
•Covers approx 5-10 sq ft
•11oz can

http://www.caswellplating.com/aids/plastidip.html