It doesn't quite match your long plane ride criteria, but I've taken two trips with Spice Roads. One to Thailand/Cambodia (over Christmas) and one to the Mekong Delta (over Thanksgiving). The company did a reasonable job with both. I notice their web site has a "tripfinder" feature where you can put in departure dates and trip specialties such as e-bikes.
Another suggestion I'll make though it doesn't match your e-bike criteria is Suriname. There is a company that will rent you bikes for self-guided tours (
Zelfstandige fietsreis Suriname | Fietsen in Suriname); help with making reservations. The country as a whole is very flat. In the winter it is two times zones ahead of NYC (in the summer one). Even in December/January it is still hot/humid so distances you'll bicycle likely won't be extremely long.