You need a sinewave for some electronic devices.
The only things that work just as well on a modified sine are heat producing items and incandescent lights (also technically heat producing items).
Motors run hotter, although most work ok on a modified sine.
I purchased one of these a couple of years ago. No frills, but it works well:
(No financial ties, just a happy customer)
OSP 1500W PURE SINE WAVE POWER INVERTER 1500 3000 WATT | eBay
Wife loves it. She can run her VitaMix on it to make smoothies, and I can run a big shop vac on it as well.