Quick recommendation - I have just bought various suction + screw applied bathroom fitments in the Tatkraft Megalock brand via Amazon, and they seem to be good and inexpensive.
I have successfully applied these to smooth tiles and Multipanels, and the loo roll holder (ie a lightweight one) to the underside of a stainless steel cabinet. I have not had them long, but they seem to be very well attached. Glass should also be OK.
I cannot comment on whether it will rust or not, or longer term use.
The obtangular (they call it rhombic iirc) caddy below us now in my bathroom, so I have bought another for the rental. it says this one is tested to 8 kg.
The caddy below is about 30cm by 15cm made from 5mm wire / rod, and is about £16.
I also have the soap dish / loo roll holder / towel hook set for about £17.
(Do we need an Amazon affiliate link for Buildhub?)
Ferdinand