another reasonably priced floating tenon tool is the Bead Lock. The floating tenon stock comes ready made, but you can buy a special router bit if you are bound and determined to make your own. The nice thing about the Bead Lock System is that you don't even need a router to cut the mortises. A powered hand drill and drill bit is all you need to make the mortises using the Bead Lock jig as a drill guide.
All you need to do to use it is align the jig to a pencil line across the two pieces to be joined, then attach a clamp to hold it in place. There are three holes in the Standard Bead Lock jig. You drill those three holes and then shift the drill guide piece and drill two more, and your mortise is cut. Do that to both pieces and then cut a floating tenon of the needed length from some of the tenon stock and you are ready to glue it together. The jig comes with several thicknesses of shims to put behind the drill guide piece for offsetting the drill guide to allow you to make an offset joint.
I had the standard Bead Lock jig and used it quite heavily for a while. With just a little practice, I was able to create some very good joints with it, but somehow along the way I decided that I had to have "real mortises and tenons" because I was making chairs with angled joints. Looking back, the only real problem was that the Bead Lock jig only let me make one length of joint, but a different drill guide piece and drill would let me make both 1/2 and 3/8" thickness mortises and floating tenons. The accuracy of the jig was very good though, as long as I was careful to align the jig to the pencil mark. I had the original jig (before Rockler Painted it blue). My original jig came with the 3/8" drill guide and a few 1' long pieces of 3/8 Bead Lock floating tenon stock.
For $30 the basic Bead Lock jig is worth buying, just to see if you like this method. https://www.amazon.com/Beadlock%C2%A...l+beadlock+jig
The new pro version is considerably more expensive and I doubt that it's new features are worth that much more, but it would make offsetting the joint easier than with the basic jig and included shims. https://www.amazon.com/Beadlock-Pro-.../dp/B00QTZM9M2
In a weak moment I gave my basic Bead Lock jig to a woodworker wannabe friend a few years ago.
Making angled joints with it, like for chairs, will require making some wedge spacers to hold the drill guide part of the jig in just the right position, but I think it can be done. I never tried doing that with it. Everything that I used it for only needed flat 90 degree joinery. I had bought it almost 50 years ago when I first started making furniture and haven't used it in probably 30 years. (my reason for forgetting to tell you about it - until now).