I had looked at something similar bu the diameters are wrong, I've also thought about mounting a cricket or snooker ball in the end, trouble is nothing obvious works.
Might need to find a metal fabricators and get something turned out of ali
Bummer.
What about getting a tube that goes slightly up and out bend into shape, that has a smaller tube inside to fit into the ends of the chassis tubing (think "beach buggy front en miniature")?
If you do it like that (or similar), you can use a small screw/hex to fasten it in each tube.
