Question about Polini kids Universal changing unit for IKEA Nordli chests of drawers with a depth of 47 cm

Practically any standard size. The "total lying area" with the top on the Malm chest of drawers is 75x75cm, our changing mat is 72x48cm (brand unknown, but "standard model") and so there is plenty of space for everything else you need in addition to the mat: Night light, wipes, ointments, soft toy,...
We've been using it for 2 months now and we love it. And tip: for taller people (>173cm), the Malm with 4 drawers is worthwhile, as it gives you a great "working height"!

You can use almost any mat size that you might have. But if you need to buy a new one, the best options are 72x85 cm or 75x85 cm. We bought a mat with the measures 75 x 85 cm and it fits very well, it sets slightly bended in the sides but this protects better the baby in case of crashing against the sides.