I can give you a little advice on putting a new knot in that 100T. That brush is the first brush that I ever had and I have put new knots in quite a number of Ever Readys just like it, but there is good news and decisions to be made.

When you cut out the knot that is there you will discover that the handle is hollow and that the knot that is in it is about 18mm or so. One of the boar knots from TGN (I think a Vulfix knot) is perfect for an original restore. If you want to go up to a 24mm badger, you can do that, but you will have to cut out the hole in the handle to a 1" hole. Not a problem, but you have to be careful to center up on the hole and then cut without breaking the plastic as you cut it. There are a few ways to get this done carefully such as tracing a 1" ring centered around the existing hole and then using a dremel with a sanding drum to gently enlarge the hole out to your tracing.

Don't fill up the handle with epoxy. It will get hot and probably break it. Instead, use something like a wine cork ( I always have plenty) cut to the desired length to take up the space in the handle so that your new knot can sit on it when you glue it in. Glue in the cork or other filler and then fill up around the cork with more filler and glue it all in so that you have a new hard surface to mount your new knot.

I hope this helps a little.

Will N.