I've just finished servicing a number of these for our club, but required a few spares. Amongst which, were a clevis. It's different from from the one I was replacing, and so is the clevis pin. These parts appear to have been redesigned to make fitting easier. The old pin is secured with a split pin at each end, to hold it in place.
These parts don't fit the older [pre 2012] pumps, though!
Old, worn clevis on the left, above
Above... no room for adjustment, without redrilling and shortening.
Lack of adjustment, means the handle does not return fully.
To fit the new clevis, I had to grind some metal off the sides, then redrill the pin holes lower down, and finally cut off the redundant section above. Previously, I had taken a couple of mm off the bottom [threaded] end, but might not have needed to. Anyhow, a couple of hours work, and it fitted OK. I did have to reuse the old clevis pin as well, as the clip on the new one fouled against the top nut on the cylinder.
Harry Masons emailed back to say that they do hold some older stock items, and to phone them for details, if required.
As a side note, these particular engines don't have a built in check valve. However, the solution is simple. They just require a duckbill valve which fits into the cylinder inlet.