Sadly, not really.
While one can physically replace the SSD unit, Apple as well as 3rd parties have not offered a new replacement SSD unit.
Here's the IFIXIT guide to get to the SSD: iMac Intel 27" EMC 2546 SSD Replacement. As you can see you need to take most everything out to even get to it. The other thing here its quite easy to damage the display just opening the system if you don't follow the steps correctly as well as use the correct tools. Here's what a damaged display looks like: Thick black stripe on iMac screen after attempting HDD to SSD swap.
So unless you can find an Apple SSD to replace yours with (used), have the skills & tools, you might find selling yours and buying another system that meets your needs just easier and cheaper in the long haul.