Delchem ball valve arm

Hi all.

I'm trying to replace the white plastic arm that connects the plastic ball to the valve on a delchem bottom entry ball valve in a toilet cistern, as the plastic thread has sheared off at the ball. I've been around the local DIY places and can only find one Delchem kit, but the white plastic arm is too long and the ball ends up hitting the side of the cistern.

The plastic arm I am replacing is approx 7" from end to end, however the only kits I can find they are about 9.5". Can anyone please advise me on a place where I can purchase the shorter arm, or a specific name I should be looking for? There's no mention on the packaging of the kits that I have seen as to different sizes - only heights. In fact, the packaging just says "Fits all tanks and cisterns". yeah right.

Many thanks in advance,
Steve

ps. can anyone also tell me the significance of the red plastic circular disc that clips into the arm? My old one doesn't have it, but the new ones seem to.

a Torbeck valve is a lot smaller, and a lot quieter.

or a fluidmaster the red do dah is an oriface in case the one fitted is too small

Thanks for the replies guys. Ended up going for the torbeck route in the end and squeezing it into the cistern between the side wall and the siphon. Seems to work ok so it'll do for now. (planning to get bathroom done soon)

For the record, about 30 minutes after buying and installing the Torbeck, found a Delchem 6.5" plastic arm that would have been just what I needed on plumbworld.co.uk for £4.

Thanks again.