If your clients want to deal straight with the sellers...what is your purpose? That makes you redundant right?
Anyway, I hope you realize this is a $8 million+ deal - if you are serious I can hook you up with a whale (for the record: I make no claim of having 1000 BTC myself - I just know people who do). However, you need to answer the following:
1. Where are your clients located,
2. What payment method would be used,
3. What rate would they consider (+3% to +5% is usually the range for bulk deals)
4. Would they require 1000 BTC in 1 transaction or can it be a "drip feed" (i.e: perhaps 5 x 200 BTC spread over every alternate day for 10 days)?