you cant
The only way is to buy one from the Poptropica Store. The ones that appear on Shrink Ray island cannot be costumized.The original Shrink Ray appeared in the ad-game for Despicable Me in June, 2010.
Watch Thinknoodles guide toshrink ray island on youtube
Because the un-shrink ray interacts with the traces of the shrink ray zap causing only previously shunk items to grow.
I am pretty sure that is almost/is impossible.
shove them off
Hide behind the round mirror.
mark
you will call a shipor you will make a boat
MrSilva has the shrink ray he is the one who stole it and shrinks you
A 'shrink' ray is imaginary . . . it does not exist, nor can one be built.
Click the red thing on the left side.
Duck under all the objects that are bigger than you.