Dear Patricia, you can get a cheap Yellow gel sealing tape, CBS Scientific from VWR Company (call to order 1-800-932-5000). 1.5''thick X 72 yds. Cat.#CBGT-72-15, $18.00 each(roll) It works great. Liuda Ziaugra DNA Sequencing Coordinator Whitehead Institute for Biomedical Research 9 Cambridge Center Cambridge, MA 02142