Pure sine wave inverters are getting cheaper.Something like this:
BESTEK 300Watt Pure Sine Wave Power Inverter Car Adapter DC 12V to AC 110V with 4.2A Dual Smart USB Ports
BESTEK 300Watt Pure Sine Wave Power Inverter Car Adapter DC 12V to AC 110V with 4.2A Dual Smart USB Portswww.amazon.com
What is interesting about the pure sine wave inverter you posted, there is a list of things that are appropriate for pure sine wave vs modified sine wave inverters:
What is interesting, is that there are many things that shouldn't be powered by a modified sine wave inverter according to the manufacture. This is the same manufacture of the modified sine wave inverter that the OP is using.
I would argue that some of those items would be fine with a modified sine wave inverter, such as the phones, laptops, and batteries.
The TV and stereo would probably be fine, except I personally noticed that using a modified sine wave inverter with anything with speakers that is AC powered an annoying hum plays over the speakers.