Well the NilJon isn't all that big - even with the radial kit. The Diamond discone and Scantenna are somewhat larger in size, and probably easier to spot. How about the very inconspicious Grove Omni? Heck, we even have something on the Wiki to show you how to build your own - it's nothing more than an off center fed dipole. The folks that have built it seem quite pleased by its performance.
You can find links for both on the Scanner Antennas Wiki
Putting something indoors will probably reduce how much you hear, depending on the construction of your home/condo/ect. An attic is almost ideal, assuming you don't have siding, metal flashing, ect. However, you could easily put a ScanTenna in a good sized attic. And come to think of it, Diamond recently came out with a mini discone - meant for mounting on a vehicle (!!)
Gotta get ready for work...73s Mike
 Looked at the link for the mini discone - it doesn't cover VHF lo, so that's out. However,the PAR MON-3 antenna supposedly works well there, even tho it's not tuned for it (at least according to the mini review Grove did). That too looks like it's relatively stelthy, so it might warrant more investigation.