Best fabric glue?

[TheCraicDealer]

Hmm, hope this is the right topic for this. I, being small of boob, need to stick some more padding into a bikini- basically went and got one of those £2 bikini tops from Primark to steal the padding and whack in one which is a bit too roomy. But there is a high chance it will, er, pop out, so want to secure it. Not enough give in the material to sew it in so was thinking fabric glue.

Has anyone got any recommendations? Needs to be able to withstand sun, sun cream and all that!