Have you tried getting an ipblock from a RIR and failed? they seem widely available if you justify it and at a reasonable price. If not, you can always go to a host and buy at a smaller fraction...
RIPE wont "sell" me an IP block, no matter how reasonable a price I offer. RIPE will gladly let me pay them LIR annual membership dues for 2 years before they consider allocating me a /24 (based on current waiting list times)
But in my RIR I don't think there's a 2 year minimum.
Regarding IPv6 blocks do those require a 2 year membership as well? They are probably easier to get.