want to seal birdbath with safe clear SHINY product ?

Help. I have grouted two homemade concrete birdbaths, and now I want to seal them with a product
that is clear (transparent), GLOSSY, and safe for exterior use. I already bought the
wrong product and will have to go back to the store. I bought a fast-drying polyurethane
that I now see is not for exterior use. Sigh. So it will have to be exchanged.

I've read many a thread on the topic, and people seem to be a bit cagey about
what they're actually using on this final step. I hope it is not top secret information.

Adhesive was the G.E. silicone for exterior use, grout was black sanded
Polycrete. I thought I could just put a clear polyurethane, let it sit some number of
days, then finish with Thompson's waterseal. What do you folks suggest? I will
really appreciate any information.