Do Silent Condensate Pumps for Air Conditioners exist?
Short answer. In my experience as an HVAC technician:

There is no completely silent condensate pump on the market that Me or my Suppliers are aware of. If there was, everyone would be buying them.

There are however certain pumps on the market that are designed to take into consideration sound level. The quietest pump i have ever come across is the DiversiTech ClearVue Condensate Pump. They have great build quality along with all DiversiTech products, and also has a built in alarm and over flow sensor that can be wired into your HVAC system to stop operation of the air conditioner if there ever is a blockage in the discharge line, or if the pump should fail for whatever reason.