Unlike the Outdoor Camera , the other wyze cameras do not have built in batteries, so that is the first problem - most of the solar panels sold for security camera does not have a built in battery, and panel size all seems too small. A camera consumes between 2 and 4 watt so the solar panel has to be rated at least 3 times that amount, since the sun only shines 8 hours a day - so you need at least a 10 to 15 watt rate panel+battery, but most of the small ones are only rated 4 watt.
Almost all solar charge controllers has a USB power outlet -- so setting up a solar panel with a battery and a charge controller is not that hard - I have 3 of these setup with different size battery and solar panel depending on how much power I need, as they powers not only my cameras but also my landscape lighting and water features.
There is also Phone charger batteries with built-in solar panel, but the panels seems to be all too small (less than 1w) for continuous use and discharge of the battery.
but when it comes to replacing batteries isnt it cheaper when you have one big ups?
No, you just need to buy a UPS that takes normal batteries. My rack mount UPS takes standard 12v 7ah batteries and so do my smaller ones. A lot of the cheaper UPS will use proprietary battery packs.
Nice, would this battery work?
http://www.amazon.com/gp/product/B003S1RQ2S/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
edit: and this inverter http://www.amazon.com/gp/product/B019IFYMQU?psc=1&redirect=true&ref_=ox_sc_act_title_2&smid=A3BVVW711G7EUD
basic PWM charge controller, $17, 7ah 12v battery, $18, 10w solar panel, $26. put it somewhere the panel can get a couple hours of sun a day, the charge controller has USB output to charge your phone.
unless you have other design goals, like trying to make it super portable and want the very minimum panel size, in which case a lot more details of your use and needs would be required.
new motor can't hurt! I bought a used power wheel and new motors helped that out but it was several years old. I'd try adding a second battery first personally.
I don't have any experience with Kid Trax but if they are anything like power wheels then the stock battery takes up extra space. I bought a 12v battery off of amazon with a new wiring harness and it has more MAH (longer run time) and takes up the same space as the stock battery.
Amazon has a replacement 12v battery with harness for 80 bucks, or you could get just the harness for $15 and a 12v better for $22 instead. I have only used the "expert power" brand and it has been working fine for me. best of luck and let us know how it goes!
harness
battery