I purchased 10 of these grip screws from SOLGW.

They are a 1/4 x 28x 1" screw made of 4140 steel. The head has a 3/16 hex plus its slotted and is finished in black oxide.

There is no visible thread locker on them that I could detect. The head of the screw is wide for a good clamping surface.

They are $2 each when bought in bulk.