IBKR clients are not able to hold a private placement investment. In general, you can only hold securities that are trading in the secondary market.
You can find available products for trading on the IBKR website, clicking on Products followed by Product Listings. You may also search the IBKR contract database through the Contract Search tool, available on our website by selecting the Support menu followed by your account type (Individual or Institution). Here you can do a Simple search by entering the product name or symbol, an Advanced search which allows you add filters to the search, or a search by specific product type.