The I-zap does not look well built, is only a single frequency, and if it was actually 10 times as powerful as most good zappers, it could kill you. Looks over-priced as well.
The Terminator-2 might be a good choice but the contacts are small and close together.
Perhaps you might want to look at some others.
I personally like the ParaZapper CC1 as it has the 15 Hz of the Terminator but is stronger, It also has 2 frequencies in the 30 kHz range, the Rife Trio (727, 880, 787), as well as three Rife frequencies in the 2 kHz range (2280, 2127, and 2489).
Please note that I might be prejudicial as I am the producer fo this product, but no one has shown me anything better.