So I have this old 9 speed Dura-Ace rear derailleur (RD-7700). That piece around the pivot bolt with the little screw on it has broken (please see the picture).

I know this comes apart. Is there anywhere I can buy a replacement piece? Or any other suggestions for fixing this?

A lot of LBS have bins of broken/used parts just for situations such as yours. If you have an indy near you (not a chain) I suggest you take it down to them and see if they can help.

if you can find that part you may be able to fix it but it is not an easy task. that spring has alot of tension.

I brought a vintage LX rear derailer with the same problem to my LBS. This derailer was a date correct rear DR for a vintage MTB I was building so I really wanted to repair it. Verdict: Yes it can be repaired, but no, it's not worth the cost.

prof2k what is the condition of the pulleys? I have an 8spd DA but the pulleys are shot. I just want to use it for chain tension on Internal 8 so I think those would work. if you care to part with them.

I don't know where you can buy the part but to remove it, you must first rotate the c-clip (more like a "u") using a small screw driver then pry it off the threaded shaft. This will release the broken part you seek to replace along with a torsion spring. Reinstallation requires retensioning the spring while at the same time reinserting the c-clip. It takes a bit of dexterity to do so and a second set of hands can be useful.

If you could remove the piece and post a picture I could see if it matches the same part on a broken Deore derailler that I have. I doubt it but you never know. Failing it, scour Ebay or post in the wanted section for a broken (just not in the same place) Dura Ace 7700 derailler. Someone must have one. If you can't find the part, send it to me and I'll continue the search

The pulleys are in great shape. The derailleur only had a few hundred miles on it before a crash where the derailleur hanger broke off and did this to the derailleur. The pulleys on this derailleur are different sized than ones on a dura-ace 8 speed; I don't know if that matters. However, I'm not quite ready to part with this, I want to try and find another broken derailleur to salvage the parts from. If I change my mind though I will let you know.

I took apart a few derailleurs from my broken parts bin, but none of them would work. One from an 8 speed XT derailleur (RD-M739) looked like it was going to work, but the size is just a little bit different. I also took apart a 7-speed shimano 600 (rd-6400) derailleur for fun, but it was nowhere close.

I think one from a 9-speed ultegra or 105 derailleur will also work, so I'm looking out for any of those in broken condition.

From left to right here is the one from the dura-ace RD, the XT, and then the shimano 600.

I found what I'm looking for. I can a whole new B-axle assembly for around $20. That includes the part I need

Where did you find the parts?

This is a place that sells them:
https://www.ride-this.com/index.php/s...ce7700-ss.html

However, I'm going to see if any bike shops in my area can order the parts for me now that I know shimano sells them.