>>6352563If you want to keep the titan master, get a 3p helmet, though all of them will look stupidly huge due to the head's size and fragility issues. Renderform has a replacement head plus some other goodies, but unless you want to pay twice the figure's price just fixing it up, you might not be into it.
If you don't mind the Titanmaster losing all functionality, you can cut off the mask and glue it on. It will fix the gap between the head and mask, plus allow you to get rid of that awful chin guard. The Titanmaster won't fit into the cockpit, but he can loosely stand on a Titan peg.
All options require you to take the head off.
My suggestion? Return it and get a 3p or wait for a better figure.