Use is_singular for woocommerce categories?

Hi there,
I’m trying to find a relatively easy way for my client to password-protect specific categories in their WooCommerce store. The only plugin we’ve found uses roles, and that won’t work since we need folks who are not logged into the site to not have access from the start. We also can’t have the items within those protected categories show up in search (that bit I think I have covered).

I found this website: Basic Password Protection Without Using Users, and I see how he’s using is_singular for this. But I’m lost as to how to modify this for a WooCommerce category. Any assistance would be greatly appreciated.

Thanks in advance.