While we don't yet have a dedicated case for the Tascam Portastudio 414, one of the cases in our UNISON line may be a good fit!
The dimensions we have on hand for the Tascam Portastudio 414 are: 14.4 x 9.7 x 3.9 inches. If that aligns with what you have, we would recommend looking at the UNISON Custom Edition: Compact: 15.1" x 13.7" x 4.7".