Sorry, but there is no way anyone is going to trade you a CPS 1000 or 1200 for an Orca. It's not because Orca's aren't good, but because they don't shoot as far and they are more awkward to use, which are 2 things that are heavily prioritized by most people on here. The MD 6000 is more of a fair trade, but those are rare, and you probably don't want one anyway unless you know how to reinforce the firing system. I read that in the vermin wars marauder's team went through like 6 or 7 in an entire summer because they kept breaking. SEAL has an epic MD 6000 that he modded, but I really doubt he'd be willing to part with that.
I'd trade you my XP 310 for your Orca, but I don't think my friends would be able to handle it that well. My old Blazer is my #1 primary, which leaves only a Colossus 2, and you don't want other water warriors anyway. Water Warriors also don't sell that well on ebay, so your best bet is probably to find someone who has an extra XP something or another lying around, or maybe something a little newer but still pre nerf SS.