276-300

[Moradin]

I can't see a way to vendor it to 300.

Silver Conduit Caps, and farm sunshard ore, Or something else good?

[melkorr]

Quick Trivial lists ftw!

Try Gem Studded Chains.

[Gaell Stormracer]

You seem to be overlooking the Velium jewellery combines - sitting in Thurgadin you can get to 282 (Velium Ruby Veil). Then, diamonds are relatively easy to find on vendors (PoK, Lobby etc) in pretty large quantities, so you can get all the way up to 290 without too much pain.

From 290 to 295, I got there in about 30 combines cutting "flow" stones I got while grinding faction in Dranik's Scar, and the last 5 points I did with the chains.