Planck
believes in Dog
Just found my order from Amazon back in 2014. This is what I bought for about $15...
White SiliconeTubing, 1/4"ID, 7/16"OD, 3/32" Wall, 10' Length
https://smile.amazon.com/White-SiliconeTubing-ID-Wall-Length/dp/B003TJ9YQU/ref=sr_1_1?s=industrial&ie=UTF8&qid=1509923709&sr=1-1&keywords=White+SiliconeTubing,+1/4"ID,+7/16"OD,+3/32"+Wall,+10'+Length
Added: I bought 10' because I expected to periodically change the whip as it got smelly and dirty. As it turns out, I hardly ever use a whip with any of my glass or vapes, so 10' was way more than I needed.
Thanks very much @cybrguy. I'll just get a couple of feet.