Lori from L2 Data Collection sent me this note on mastic –
I’m not sure where you buy mastic, but we have been
purchasing it from a company called Mar Mac in South Carolina. (843)
335-5814. Much cheaper and it is the same tape we used to buy from Jamar.
We gave up on mastic because it is very messy and somewhat expensive. We've had good luck just taping our tubes down with duct tape. Our favorite is Gorilla brand duct tape, which is cheapest at Home Depot.