I don't think I've seen this mentioned anywhere, it could be useful to someone.
I picked up a GT steering wheel without a horn push fairly cheaply from ebay. I like the three spoke design but I'm not building a GT clone so I've never intended to pay the astronomical prices a horn push/complete wheel can fetch.
I got the centre for a Volvo F88 wheel for a tenner thinking it looked about right and I could fiddle with it until it fitted. It's actually made by the same company who made the GT wheel and they seem to have used the same basic pattern so it clips into the wheel ok, the horn spring from the centre makes contact with the wheel ok. The bezel is slightly larger than the GT wheel (~2mm dia.) and the chamfered lip on the wheel prevents a tight fit.
These photos are of it just pushed on roughly. It's difficult enough to remove that I'd be happy driving with it. A bit of fiddling and it should look ok.
(p.s. I'm looking for a spare
plastic collar from behind the steering wheel
)