Have you heard of anything like this in Switzerland?
Hi! We are looking to buy a flat in Kanton Zurich. Our experience in The UK is that there are independent bank agents who help to search all the local banks to find the best mortgage option. They receive a commission from the bank after successful initiation of the mortgage and there is no fee for us as the buyer.
moneyland.ch and comparis.ch compare mortgage rates on their online platforms:
https://www.moneyland.ch/en/mortgages-comparison
https://www.comparis.ch/hypotheken/default
News media have reported that insurance companies are more competitive than banks for some mortgage products due to the fact that they are generally not subject to the SNB's negative interest policies.
Those 'Agents' used to sell a high commission paying insurance policy, nothing in life is free, it's often better to pay directly for a service.
As suggested above Comparis is a good start.
In my anecdotal experience you can look for the best quote on there and then take it to your existing bank or insurance company and ask if they will match it or beat it. Both my bank and insurance company said they'd beat the rate... and then tried to beat each other. It was hardly a price war but did mean 0.1 percentage point better than the best on comparis
So play the market as much as you can and by doing this yourself you'll cut out any middle agents and their commissions which have to be paid somehow.