@ricks - Lots of plastics vendors, and some who sell DIY flavorings & other supplies, carry those twist-top caps. You need to know the specific neck type/size of the bottle they'll go on though, to order them. Most come as 18-400, 20-400, 22-400, 24-400, or 28-400. Some bottle necks are 18-410, 20-410, 22-410, 24-410, or 28-410, too, because the
threading is slightly different on them. Unfortunately, most vendors charge an arm and a leg for S/H, which is usually
a minimum of $8-10 for a small order. You might also want to check Amazon, but again, you'd have to know the exact neck size caps needed.
IF you can determine what size you need though...I might be able to help you with a small quantity of them. I have multiples of several sizes.