some of that UV activated plastic-glue stuff? I got a tube for about $5 from a dodgy chinese website - it works a treat!
http://gizmodo.com/super-glues-got-nothing-on-this-liquid-plastic-you-hard-1666641845
Although it is best used indoors; the sun's UV rays are enough to harden the plastic. The cheap UV light is pretty weak on my tube so I just leave it in the sun.