My HB had them. They're DIY fittable. Inertia reels bolt through the back shelf (sitting unsightly in view which is why I removed
them), other mounts go under the seat.
I think I've still got them (3 complete belts if I remember rightly), assuming I can find them I'd sell the *whole* kit to anybody
interested for £30 including postage.
*One* belt costs about £40 new on the internet, so £30 for 3 is quite a bargain
Sid