there is no specific product. when i had a leaky crack due to the shower head falling in the bath, i initially used super glue. Later i added a flexible, waterproof, clourless glue from unibond (extreme glue) and it has done the trick. TIP - if you have kids then buy a shower head with a plastic head- its gonna get dropped in the bath loads of times.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix baths and showers.