You need to look around in various archery shops. There are lots of adjustable sights on the market that are good for hunting and work well for target/3D, too. HHA is one of the more popular series and they have at least 1/2 doz models. Almsot every sight manufacturer makes one, too.

I suggest you use the search function and type in "single pin adjustable" or "slider sight". You'll get enough info to read for a month.

That being said, I concur that any sight I choose has to be machined aluminum. I've had my share of cheap sights over the last 40 years and IMO plastic has no business on a sight.