Does anyone make a passive case for a NUC that is much smaller - all of my content is on my server so I don't need anything more than a mSATA drive in an HTPC. Assuming that you could make all of the connectors fit you could make the case about half the size of this one.
The standard Intel NUC case is 116.6 x 112.0 x 34.5 mm or about 4.5" square, 1.5" tall (with feet).
All-passive NUC cases include:
Akasa Newton -- several for different gen of NUC boards, all 150 x 170 x 47mm.
Streacom NC1 -- 150 x 112 x 48mm (W x D x H) -- this one actually has the biggest fins, so it might be the best cooling.
Tranquil PC Abel H2 -- no dimensions given; it looks like it would be wider than deep, a bit like Streacom's.
Both Tranquil & Streacom are pricier: 80EU & 99UKP, iirc. The Newton is available in the US for ~$85.
Or.... if you have some metalworking skills, you could roll your own. It's just a piece of extruded aluminum clamped to the CPU/GPU. The rest could be formed of metal mesh. Doesn't need to look fantastic, can be just tucked out of sight, use a wireless kb/m. Materials cost might run $20.