Eyes are everything on a puppet head. Get them slightly wrong and the whole build looks cruddy, no matter how good the sculpt or the paint job underneath. There's no faking it and there's no getting round it. You just have to find someone who can make good eyes.
The UK used to have a company for this called Brambles. They were the people everyone went to — film, TV, taxidermy, even real prosthetic eyes for people. Everything hand made. They'd lase velvet veins straight into the glass and tint, and you could ask for any iris colour, any pupil shape, any size, human, animal, or dinosaur. It was a small family business with a genuinely rich history. You didn't just place an order — you booked a consultation and worked it out with them from there. Then, with a reputation that good, the cost caught up with them, and sadly they went into liquidation. I believe they might have come back in some form since, but that didn't help me at the time.
So I cast the net a little wider. I found a company in Germany that specialised in taxidermy eyes. I ordered a catalogue and everything in it looked amazing. But it was all glass, and I wasn't sure it was right for what I needed.
Then somebody mentioned a place in the US — the company that makes eyes for theme park characters and films. I reached out, and they looked exactly right. Resin, not glass, which meant they'd travel better and hold up. Convincing too, the way they caught and reflected light. They offered three tiers: basic, more realistic, and ultra. Each tier roughly doubled in price, and the detail scaled up with it.
I put in an order on the base tier. Four sets. Start cheap, see what turns up, and go from there.
Now it's just a case of waiting for a box from across the Atlantic and hoping the catalogue didn't lie. I won't really know until they're sat in a head, catching light under a rig. If the base tier isn't good enough, at least I'll know precisely which corner I cut, and what it costs to un-cut it.