What would you recommend to turn this into a fixie?

Just got a reply from velosolo.....won't work.

Regarding the spacers on the rear we often get asked if our SS spacers are compatible with Campag hubs - they are not designed for Campag but some riders have used them successfully. Unlike Shimano, Campag have changed freehub OD dimensions over the years, the ID of our spacers is 35mm so please measure your hub with a vernier guage if unsure. We do not have any Campag specific cogs I am afraid.

It's a shame since the hubs are fine. The quest continues.

So long as they are plus of the OD of your hub, you're fine. I just made some from cut pipe - doesn't have to be precision engineering as once it's all tight, nothing near the right size is going to move, so long as you cut square (use a jig).