Louvers are small and wouldn't add much weight if done right. I would carve/whittle/make one louver, cover it with some oil so it won't stick to anything, then press it into some heat-hardening sculpting clay from a craft store. Carefully remove the carved louver, put the clay in the oven, bake to harden. Then using the sculpting clay mold you just made, press some sculpting clay into the mold and make as many louvers as you need and bake them in the oven to harden them.

Then there is always stamping them in aluminum with a steel die for the purists. But is you intend to do that you already know what you are doing and have a lathe and mill.

Planeman