I had the same thought when I was $450-$500mil. Big portfolio, but never enough disposable cash. What I started to do was focus on films that either do or are likely to get a release date. It tooks about 18months (as I still wanted value for money and didn't want to just buy for the sake of it).
Once I "caught up" to where I owned shares of films releasing into theatres on a regular basis there was always plenty of cash coming in to fund the next IPO or long-shot punt (which are usually cheap anyway).
The other thing I did was to purchase starbonds that were cheap of people in high-profile films and sit on them. I try to use a ratio of making triple my money back. A great example is Martin Freeman. His price is still $10 but he's in the next 2 HOBBIT films releasing. It might take a while, but it's only a $200,000 investment that will net me about $100 per share. It's a great "set and forget" stock. My current port is $700mil+ and I have about $35mil in starbonds that are all cashing out on a regular basis at over triple what I paid.