how can I store extra product-info for admin-only view?

Greetings:
I would like to include info in each product, that is to be different for each product, viewable only by admin, so that I can easily find where to reorder products. I want to include a list of wholesale suppliers that offer the product so that I do not have to go re-searching for that info again later.

As a quick fix, if you don't have any 'product URL's showing on your product page (a link to a manufacturers website about the product) you could stick the information mentioned above in that field.

Is there anyway to easily insert a text field entitled "Product Notes" that could be switched on to public view or switched for admin view only?

I don't know about "easy", but the process is described here: How-To: Add new Properties to your Products

I presume that you could set the field's public visibility in admin > Catalog > Product Types > Product-General > edit layout.