How about:

Extra batteries---good thought

Emergency blankets---got lots of the cheap ones that have been replaced by heatsheets.

First Aid Kits I've got a bunch of keychain first aid kits that i could include. I've also got BINS of guaze and 4Xs etc but just couldn't bring my self to sort that out. maybe a compress in each tho.

Roll of cordage---hanks of parcord i can do, maybe lengths of builders string?

Reusable bottle (the cheapest route for this would be to have on hand a supply of empty CLEANED gatorade type bottles)---I had an issue with this one myself. Give them a reused bottle of gatoraid(or similar,I'm just thinking clear with a wide mouth), might look odd. Or buy an extra couple of 1.5L Dasani (strongest bottle out there) every shopping trip.

For yourself, definitely expand your own preps. Others have made some great comments already. Anxious to see how this thread develops.