The building and commercial vehicle industries have moved from butyl tape to 3M VHB tapes and it's what Andy at Boatworks Today recommends for bedding port lights. Because it's become so widely used, availability and pricing are good. There are various thicknesses, widths, and formulations for different uses as described in their product sheet:
I still have some butyl tape to work my way through, both gray and black, but when gone I'll probably switch to the VHB.
btw - I am environmentally conscious but the EPA required changes can sure be a pain. The latest to hit me personally is that Home Depot and Lowes no longer carry MEK. Yes, it's a nasty chemical to not get on your skin but it'll cut things that acetone and other solvents won't touch.
I still have some butyl tape to work my way through, both gray and black, but when gone I'll probably switch to the VHB.
btw - I am environmentally conscious but the EPA required changes can sure be a pain. The latest to hit me personally is that Home Depot and Lowes no longer carry MEK. Yes, it's a nasty chemical to not get on your skin but it'll cut things that acetone and other solvents won't touch.