Other than STK, are there any commercially software packages available to model changes in orbital parameters due to increases/decreases in satellite drag. I am trying to figure out if aerodynamic drag can be used in LEO for orbital maneuvering.
One of the problem with drag models is that most are not very precise. The few which are precise are usually written in FORTRAN, and lots of tools just interface with the FORTRAN code instead of rewriting and re-validating the algorithm.
The typical high fidelity drag models are the Jacchia Roberts models and the more recent NRLMSISE00 model. The former is only available in FORTRAN to my knowledge. There is however a validated NRLMSISE00 model in Julia: https://github.com/sisl/SatelliteDynamics.jl . Documentation is available here: https://sisl.github.io/SatelliteDynamics.jl/latest/modules/earth_environment/nrlmsise00/#NRLMSISE00-1 .
I add this here just for completeness: The General Mission Analysis Tool (GMAT) also can model the spacecrat drag. GMAT doesn't belong to commercial software, but it is available.
GMAT has two atmospheric models in its stock distributive: Jacchia Roberts, which can be used for altitudes more than 100 km only, and MSISE90 (for any altitudes).
Copernicus probably also do the similar things, but it seems available for NASA contractors only.
The main commercial competitor to STK is FreeFlyer. They're actually having a users conference right now, which you could join at https://ai-solutions.com/ffuc2020/
Another free tool to consider is Orekit, from https://www.orekit.org/
Drag modeling is seriously hampered by the lack of attitude information. "High-fidelity" only applies to modeling the atmospheric density. The shape of the satellite is ignored in every implementation I know. The object is universally treated as a sphere (the "cannonball model"). The farther from spherical a drag-feeling body is, the less well any atmospheric model, no matter how good, will be able to do. I have used detailed satellite models (how big are the solar panels, what direction do they point, what color are different parts of the surface painted, etc.) to compute solar radiation pressure, but I haven't seen anything like that for drag. If there is a way to do it, I'd like to use it!