EMPI 16-5103 Urethane Shift Coupler ($15 off of eBay).
I first tried putting the tube in from the right-hand side…
…but the left-hand side works better, because you can get the spanner in on the right. You need a 10mm and an 8mm for the square bolt at the back.
The rear bolt has a hole for a safety wire, so let’s do that.