One cost effective way to do it would be to get a knot from The Golden Nib and fit it to some sort of handle. I built 22mm sliver-tip for just around $20.
Here are a few handles I put together. It's a lot easier if you have a drill press, but if you want one of the two green handles I can send them to you.
You might also try talking to Rudy Vey, a member/vendor here at B&B. He just finished a restoration on an old Kent of mine and did a super job. He sells custom brushes using TGN knots at his own site and through shaveabuck.com. Great workmanship, great knots, and the prices are around what you're looking for as well.