I am making an e-commerce website for an eye-wear client. They have three types of products, namely - Frames, Sunglasses and Lenses. Frames and Sunglasses can be bought freely but Lenses can only be bought if a customer buys any Frame, or some specific sunglasses with power available. Customer can choose to buy these eye-wears with or without Lenses.
When choosing a product, they will have the option to choose from different types of lenses. Lenses won't be available either in catalog or in the search.
What do you think is the best solution for this case? I am already aware of this question, but is there a better solution using Bundled/Grouped/Configurable products? How would you go about solving this?
Update
As per @Marius's suggestion, I have implemented the grouped products. It works flawlessly in front-end. Screenshot:
This is exactly what I wanted. However, I am facing some trouble in the backend now. For some reason, I am not being able to enter Stock Quantity for bundled products. Please refer to the screenshot below:
and the grid shows zero stock, yet the product is available in front-end.
If I could somehow specify the stock amount in backend, it would have been a perfect solution! Thanks for the help so far.