One of the smallest tools we've seen that includes a chain tool, the Syncros iS Cache 8CT Multi-Tool has you covered for most emergencies. It's ultra-slim and well built from hardened steel.
T30
T25
5mm Hex
4mm Hex
3mm Hex
#2 Philips
Chain Tool
Chain Link Holder
Forged and Machined Hardened Steel Bits
Steel Side Plates
Corrosion-Resistant Finish
Weight – 82g