I recommend looking into high pagerank services as these are still the most effective types of links you can buy. Theres a reason that Google always tries to take them out, because they work. The crappy low quality links? They can do a simple algo update and crush those (like they have).
However most of the effective services are underground these days, atleast hthe high pagerank ones which matter most. In this case asking the right people can probably get you a referral. Private and referral based networks (blog or homepage links) are your best bang for the buck.