My recommendation would be
Hhampuz or
Yahoo62278, they are probably the most respected bounty managers here. DarkStar_, mprep and LoyceV are also at the top of the list, but I don't know if they still accept new bounty projects. Surely there are many respected bounty managers I missed, but I cannot mention them all here.
However, if you want to see other managers that are available, these threads may be helpful:
Overview of Bitcointalk Signature Anti-Spam Campaign Managers by pugman
Find your managers by OcTradism
[LIST ] Campaign Management Services by Ratimov