There are a few different ways you can approach this.
First, you can try to find existing lead sellers. A lot of websites just collect lead data, then resell them to people like you. You can find them online and call them up, or you can go to conferences like Ad:Tech, Affiliate Summit or financial-specific conferences to meet lead generators. You're always better off having a direct relationship with the lead generators, rather than going through an intermediary.
You can also try getting in touch with affiliate networks directly. For example, T3 has a huge base of financial-based lead offers. They may or may not be able to sell you the leads themselves, but they might be able to put you in touch with their vendors who do sell leads.
You could try building your own lead gen page and buying your own traffic. You can also try creating your own offer and taking it to affiliate networks. If you're trying to craft your own offer, be prepared to put $10,000 to $25,000 down just to get started. Lead quality monitoring is key if you take this approach, but do it right and you can get tons and tons of profitable leads.