My second gear synchros seem to be going bad and I want to swap my transmission to something different. I have a 420a engine and don’t know what possible swaps I can do. I was thinking something from the SRT4 line if applicable?

Replacing the synchro isn't too terrible of a job. I have posted the rebuild manuals in the article section of the forums and have done the job myself multiple times. The first time I didn't know what I was doing but it still turned out good. So I would go for that rather than getting rid of the transmission. There really isn't much to gain with a swap unless you find something with really low miles, or if you wanted to change the gearing with an alternate model.

Gotcha, whats the rough cost of replacing the synchro? And if I chose to swap it could I put the trans from an srt4 in?

There are some Neon transmissions that will fit, but unfortunately the SRT4 transmission will not.

PT Cruiser Transmissions are a direct swap, except the VSS may need to be changed IIRC. Finding a 2GNT replacement trans is next to impossible. I would just replace the synchro myself if it were me.