Sugru - hack things better
sugru.com
sugru.com
This is put so well I don't know what to add to it.
They had different pack options, but I think all the options were the same price. I got the option 1: 5 X 10g pack and 5 X 5g pack all for 7GBP. They had one option for one 100g pack, so the others were probably combinations between 75g and 100g total weight.
edit:
http://www.craft-products.com/polyform-plastic.asp
http://www.wisdomking.com/product/aquaplast-t-18
seems to be called "moldable craft plastic" or similar
I know firsthand that JB Weld is horribly messy, and smells bad as well.
Maybe they fixed those problems?
Its properties are here : http://sugru.com/about/ : and even to my first glance it seems completely different from JB Weld. Did you bother to look at the web site before asking your question?