round fork heads

Weird frames are interesting, I have been using a Chinese wire frame (dankung style) with plugs for band testing as there's nothing quicker for changing length and find that surprisingly easy to aim for me.
Also been making some naturals with flat/straight cut but round tips and the bands definitely pull back in a clean line from them.

If using wire I would suggest threading the wire ends for the ball's with the addition of adhesive. Confident wood will manage non-magnum bands Kalevala does plenty of destruction testing wood beads, but be safe. Also think low tips is a good idea so very square bends in the metal. If you know someone with a lathe some of the engineering plastics would be a good choice for the balls.

Might be entertaining to see it made with pool balls.

It looks from the second drawing you could somehow make a Star Wars themed one reminds me of some of the ships.

Have fun building.

Would not be as rewarding as doing it all yourself but if you did find one of the wire frame plastic grip frames cheap on eBay could be a quick modification to fit balls.
Or if your just interested in playing with the shapes mild steel can be bent very easily in a vise with the assistance of a butane torch and adjustable spanner, won't be as strong/long lasting as stainless but it's easier to work with and cheaper. Just look for 8-10mm not 6mm.

Depends what you want to spend Vs make at home but you can actually buy replacement in knobs for the ends of levers, I was looking for a different a project and found some.
That's UK eBay but sure regional ones will have the same mass produced stuff.