In the 1990s and early 2000s several swords were sold at hombu based on dimensions and instructions provided by Hatsumi-sensei.
All have longer than normal tsuka. Another nice thing about these was they came with extra-long sageo,
Standard generic iaito
Tsuka:29cm Blade: 73cm
Kukishin Ryu iaito
Tsuka: 32cm Blade 76cm
Shinden Fudo Ryu Iaito
Tsuka: 32cm Blade: 87cm
Togakure Ryu Iaito (Ninjato)
Tsuka: 32cm Blade: 55cm
Measurements were taken with a tape, so they might be a little off.
Thank you to Alex Meehan for sharing the above information.