I have been using this and it has worked well for us. I use any plate/bowl and saved a bunch of money.

Kidsme Stay-in-Place Placemat, Green https://www.amazon.com/dp/B01FDM155I/ref=cm_sw_r_cp_api_glc_fabc_qYL1Fb2FVVY7K?_encoding=UTF8&psc=1