Product Pack management

[aloevera-bm.com]

I have three products that I sell as stand alone products. I want to combine those three products in order to fit the pack version of them. One of those three products comes in a 500ml bottle. But the same product in the pack version (has its own package) comes in a bottle of 150ml. The 150ml bottle does not selling as a stand alone product. It is available only with the pack version.

So I can not add in the pack version either the 150ml bottle because I don't sell it as a stand alone product and I don't have it in my catalogue or the 500ml bottle because it is not the correct product of the pack version.......

How can I make the pack version without my 150ml product appear as a stand alone version product in my catalogue?

Thank you in advance for a quick responce...