OK sometimes the simplest things can become the most painful. Finding simple A4 grid paper online took me to several commercial sites, sticking ads and cllickbait in my face and wasting my time behind paywalls. So I took a few minutes and made some of my own. A4/A3 5mm grid and isometric paper. Includes 10mm border and a simple titleblock. Send me request for any changes.
Mr Sully's Blog 