You can get an EighthInch Scrambler frame for around that price. It's not THE BEST frame around, but for the price, makes a good beater solution. I had one for a while. Worked fine.
You might not be able to use your current parts on any modern fixed gear/track frame though. Once you add up all the parts, plus the tools, and time you need to spend on it, it will come up to maybe twice that. Maybe you can look into a cheaper full bike, like the ones at Bikes Direct. Kilo TT, Motobecane Track, etc.
I know. Bikes Direct gets mentioned a bit too often here. But ****... is there any other solution out there with similar options and prices? Show me one and I'll STFU about BD.