I have a 700r4 with Trans-Go parts and an Edge 2800 9.5" converter.
What are my options regarding a trans brake or something that'll work like one?
Doesn't seem like there really is much in the way of an actual trans brake on the market for a 700 slush box.

Not too many transbrakes available for the 700R4 because it's not a good drag racing transmission.

What options do I have short of replacing the trans?

I know Art Carr, and I believe Rossler, offer a T-brake manual vb/set-up for a 700r, but both require internal mods(complete diss-assembly). Since (like a th350) low gear is reverse in a 700r, you can't simply divert fluid between low and rev like you do in a glide or th400.

Honestly, if you are really at the level of needing a manual vb and trans-brake and OD, I'd talk to someone like Gear Star about a t-brake/manual 4l80.

Maybe i'll just wait until I break this one. I just had it rebuilt and beefed.

All transbrakes require internal modifications to the tranny.

Depends on what you consider "internal". A th400 can be done w/o pulling the pump or guts, but you have to make some cuts in the case passage ways, so it's reccomended to be apart for proper flush out. - Most full manual tb valvebodies eliminate the intermediate band and servo, but if the band is left in the case it simply won't do anything.

The TH400 kit I had needed a small hole drilled in the direct clutch hub to allow the fluid to dump quicker or something like that. A seal inside the clutch hub needs to be removed. The intermediate band and servo are removed.

I was using a B&M four-O transbrake but they all work similarly.

http://static.summitracing.com/globa.../bmm-21003.pdf

A full manual valve body doesn't need internal modification but a transbrake one does.