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.
We have started using this brand of tape.
You can get it in many different widths. We are using the 3″ wide. If you buy a large enough qty. it is about 1/2 to 1/3 the price of Gorilla brand and is just as sticky.