Do they exist, and where can I download them?

Besides what was included on the game disks, you aren't going to find them in better quality. Perhaps Activision was given higher quality music for the original soundtracks in Reignited Trilogy, but that's just wishful thinking.

I also hope for this as they did go to Steward Copeland's studio. Wouldn't it even be crazy if the original music supported the "Dynamic" function too?

Dynamic music was originally planned for the original game but was cut due to limitations I guess.