Hi,
I agree that there seems to be no cbasen for aug-cc-pVTZ available. However, since aug-cc-pV5Z is available, you could always run using it as using a more accurate cbasis will surely do no harm. Of course there will be some decrease in performance in relation to optimized aug-cc-pVTZ cbasis. But maybe some higher angular momentum functions could be cut off from the aug-cc-pV5Z cbasen if the computational cost becomes unbearable (probably not)?
Antti