Quote from OneChicago:
We have talked with ThinkorSwim several times about offering the product.....as well as Optionsexpress and Ameritrade and TDWaterhouse etc.
Remember that SSF offer improved financing for the CUSTOMER and not the brokerage firm. They will act in their own economic self interest which is participating in loaning you money on margin at rates that exceed their own and keeping the interest on any credit balances produced from short sales AND using your stocks to loan out for their profits.
Using SSF you can reduce your finance costs and actually participate in the Stock Loan profits by buying SSF under fair value.
Best
talk to openecry.com (ask for Rick) - they are rather flexible about things like linking with collective2, when other brokers don't seem to interesting in trying new things.