IZIP Trek Enlightened, Throttle?

Tinker

Pedelecer
Aug 20, 2010
116
2
SA39
On an outing to the Forest of Dean my wife met a girl with an identical IZip Trekking Enlightened except that her bike had an aftermarket throttle. Apparently it was fitted by the dealer she purchased the bike from (new) & she jotted down the details on a scrap of paper which, as in the law of sod, is now lost.
I know the varying views on throttle legality etc but I have one on my bike & she would very much like the extra boost to avoid the 'wobbles' when starting.
Please can any-one give me any information?
They seem to be easily available in the US but we are off with the bikes in a months time, she's happy with the bike and it would be a shame to change it if one can be fitted.
Thanks