A simple HD600/650 cable made with Sommer Cable SC-Square 4-Core MKII. The cable can be purchased in the US at Have Inc ($0.77/foot). Have Inc charges a ridiculous $14.20 for shipping, so, ug. You might be able to get it from jed.larson@sommercable.com for the same price, but cheaper shipping.
What drew me to the SC-Square cable is strand count. 102 strands per conductor to make 24AWG. I don't know why, but that caught my eye.
At any rate, the cable is simple and flexible. It's stock to the Y, then two connectors to each cup, sleeved with nylon multifilament. The connectors are $13 from ebay and are pretty slick.
I need to remember that 18" is probably too long from the connector to the Y.
Cable cost:
Cable: 6.05 + 7 shipping = 13.05
Connectors: $13
XLR Plug (Neutrik NC4MXX-B): $4.51 + $7 shipping = 11.51
Heatshrink and nylon multifiliment: $2
Grand total: $39.56