PERSONALLY I like the SS better, more durable than plastic, and if you get something like the Kleen Kanteen (only plastic is the stopper) you could boil water in it. OR as you indicated, the GI or GI type (probably be the same size if listed as 1qt. would fit in the SS canteen cup.
If you’re not Paranoid, You’re not paying attention Be a Sheepdog JYD#105
