Jboggs
I assume your purpose is for use in education. My 3D experience is with Solidworks. Most versions of the software come with a feature called Toolbox, in which a user may build their own model library of everything from fasteners to O-rings and Retaining Rings (and more) based on selected international standards such as ANSI, ISO, DIN, JIS, and MIL. It even includes machining features that will allow the user to add O-ring grooves or Retaining Ring grooves to existing part models based on those same standards. The user has the option of creating models of each individual part or setting it up to just add configurations to existing part models as they are required.
I already mentioned the availability of 3D models from individual manufacturers. I think it would be very good for your students to learn about interfacing with those manufacturers. They should learn about selecting a product from a catalog.
In fact I would STRONGLY recommend it! Here's why - a rough perusal of this forum will reveal MANY questions from newbies asking how to do this or that, or how to use a certain product, or what kind of options might be available. I have found that MOST new engineering graduates seem to see Google as their single, solitary source of information. If it's not on Google, it doesn't exist. It never once crosses their mind to actually pick up their ever-present phone and CALL the manufacturer to talk to a live person. How many times have I informed them that all those manufacturers have Application Engineers whose only job is to make sure your use of their products works correctly? How many times...?
I think you will find that generic models of those commercial items will be inaccurate at best.