Hi Elizabeth
Lead acetate was used as a clarifying agent for cider in west country England in the 18th C with the natural consequences. Its use was replace with simple floccing agents such as ising glass in the 19th C.
In the lab process you describe, the simple use of a couple of drops of a dispersion of an organic polyamide flocculant (e.g. Superfloc products of Cytec) followed by filtration or certification would give a perfectly clear non-toxic syrup, but it might not be as quick to work as the lead acetate.
Best regards
Peter