Sorry, I never heard of that filter so I can't give it to you or write it for you. You'll have to hope someone else has is and is willing to give it to you (check the File Exchange), or you can hire someone to write it for you, or you can start writing it yourself.
as per my knowledge, In MATLAB there is no inbuilt command for Gamma tone filter. (gammafast.m, makeERBfilter.m are third party function written for GTF by researcher. You can also use them for your reference)
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.