If you call a local steel supplier, they will cut the length you need to fit in the banjo. With this method below, your tool post will need to be 1" less than the TOTAL length of your original tool post from top to bottom. DO NOT measure just the post, this method may need a longer post to offset the "head". Then place the 3/4 (1'?) rod in your scroll chuck and drill a hole 2 drill bits smaller than 1/4". Now tap the hole to 1/4"-20tpi. With that hole, you can now take a piece of angle iron, drill a hole in the middle, and bolt it with a grade 8 bolt to the rod, using a external tooth lock washer to keep it in place.
If you like, in fill the angle iron with wood by drilling a shallow relief hole for the bolt head, and two smaller holes on the ends, close to the corner and on the bottom. Clamp the wood in the angle iron and drill the holes in the wood. Secure with a small pan screw. Now flatten the wood from edge to edge to fill the tool rest. You can skip the wood, but it looks and feels better with it.
Kinda like this, but I did not like the rounded profile and made them all flat so the wood looked like a "V" filling the angle iron.
PS, round the inside corner of the wood for a flush fit.
