I’ve used a Lencent travel adapter to power the Slate 7 for more than two weeks with no problems. I’ve used it previously to power my Beryl AX.
Mine says 20w (not 25w). I have this dedicated for the router and I don’t connect it to anything else at the same time.
https://www.amazon.com/International-LENCENT-Charging-Worldwide-Australia/dp/B0BNPJL53V