If you use silicone adhesive as Hymie says it will need supporting temporarily. That is easy done using duck or gaffa tape. Have used the silicone below for years on end and it has never failed.
https://www.screwfix.com/p/evo-stik-sticks-like-sh-t-adhesive-290ml/22070
Have you thought of fixing it with double sided tape .. this one works a treat. I have fixed no end of 3-5kg. glass boards with it.
Clean the area thoroughly before you do anything. You would stick it onto the back of your dispenser, then cut around and remove the excess. I use a scalpel to trim. Remove the backing tape and place it exactly where you want it on the wall on the wall.
With the tape you are left with a very handy that can be used any time in the future. With silicone you will be left with a whole tube that will go off in time and is of no further use !
Amazon.co.uk User Recommendation