I am not a pilot so this suggestion may be off the mark as I don't know much about the plane delivery business.

Could you work out a raft exchange with a fellow pilot or company. You fly the raft one way and the other party flies it back the other way. Depends a lot on the frequency and locations of your deliveries. You also offer the raft as a purchase option on your bid. Position it as a value-added service. Perhaps you could even work out a deal with a manufacturer as a distributor.