This one is worth a shot at the price:
http://www.ebay.com/itm/151629758964?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I got 3 and am quite pleased with them for 15mm, might be a bit small for 25 though, but no smaller then some of the suggestions made. You could convert it into a drone.
Well, the Robogear cockpits are the right size, if the rest of the craft a bit dwarf, of the super-deformed variety.
However, ugly, simple, and damn good price; that DOES seem the ticket! If only they could actually reduce shippage for quantity...
Heck, looks as if you might take a Robogear cockpit and put on the 4d ship, at which point, if you've a use for some other Robogear parts, say, a two- or six-legged walker base, they reused some of the parts throughout the Robogear series.
Sorry, now I'm probably just getting silly.
Doug