Simple (cheap) extension for RBK852 wifi network?

Thanks Furrye38!

My home is approx 450 m2 -> 4.900 sq feet. The router is one floor down from the bathroom with the weak signal, so vertical maybe 10-12 ft away, and horizontally 5ft - but on the other side of a brick wall with electric wires running through it. Like the bathroom, it is in the front of the house.

The satellite is also one floor down from the bathroom, close to the ceiling so maybe 5 ft vertical but 15 ft horizontal, with again some walls in between. It is in the back of the house.

Moving either the router or the satellite to a different position is not really an option, as I need the Wifi signal to extend both to the front yard and the back yard, and the satellite near the ceiling actually is right under my office so provides excellent Wifi6 in my office.

I indeed am looking for a down-to-earth wifi extender or repeater but don't know what would be compatible with the RBK850 set. The EX7500 indeed is cheaper but still more than €100. Acytually, the cheapest range extender on the Netgear site is the EAX15-100PES Wifi6 (!) extender that costs €99 but might be too new to order at this moment in time. Or the EX7300 that is on stock for €89. But I actually am hoping to be able  to use a way cheaper AP...