Repair tape - mouldable and yet solid setting

I can't see from your picture if it's Keeleazy but if it isn't, you might want to check out Keeleazy keel strips which people put on sea kayaks in particular. It comes in long lengths and various widths. I haven't used it so can't vouch for it, but I see it on a lot of kayaks.

https://www.aswatersports.co.uk/shop/parts/kayak/other/keeleazy-keel-strip.html

It's not keeleazy - that seems to be softer than this when set.

Does anyone know of a similar product

One way to find out possibly - ask the seller for an MSDS / Safety Data Sheet 🙂 The purpose for that is to outline if theres any health / fire / environment risks associated with the product which you'd need if you were using it in a work context - but it also therefore tells you exactly what the material is and that might help you search for it sold in different sizes intended for other applications

Or just ask your local neighbourhood astronaut

https://www.nasa.gov/offices/oct/home/tech_life_fixing.html

However, I would prefer a longer strip if I can.

Measure up the overall length you want, and the width, check the length and width of a pack, then get several packs that you can accurately measure and cut cleanly with a steel straight edge and stick several short lengths together end to end to get the length you want overall.
Might well be easier to deal with shorter lengths when applying them, as there’s less material flopping around to get stuck to other things or itself, and get dirt and dust on. Measure and mark the surface with a Sharpie, then run a strip of masking tape along to act as a guide; if you tack short bits of tape to the protective stuff and the masking tape before removing the protective backing, you can hinge the stuff back out of the way, then once it’s all perfectly aligned and butted up together, all you do is start peeling the backing off along the inside edge against the masking tape, then you can start to fold it back over, while peeling the backing off and pressing down as you go.

Keeps everything together and in the right place, with no risk of sticking too much down at once and it creasing or folding.

Sounds complicated, but isn’t really; measure twice, cut once, as a wise man once said. I’ve done much the same thing many times over the last year, and it makes a huge difference to the end result, especially if you’re doing it outside, and it gets a bit breezy.