If you take the seal out, look carefully, there should be a number on it. You may also get a seal from Bert"s or one of the other suppliers. If you can not figure it out, see if there is a bearing supply house in your area. Take the sector housing and the sector shaft to them and they will measure it and get you a seal. Not all the sector housings with needle bearings use the same size seal so you need to know what you have.
If you still can not get it resolved, if you measure the bore in the sector housing and the depth where the seal goes, I will get you a P/N of what you need. If your sources can not deal with that, I can get you some. I deal with a industrial bearing house on a regular bases. PM me if necessary. They are not expensive at all.
Chris.