Here's a pic Max. Measures approx. 45mm overall across the bottom edge in image.. or 38mm across the bits that plug in along the same edge if that makes sense.
I'll need to get some other spares anyway; twist on pump adaptor, valve, valve cap (valve tool needed?) I think these are all the same Halkey Roberts valves??
Well I've only needed a couple of bits and those came from the Honwave dealer. Parts like these stringer caps and a hose with twist on valve connection to fit up for my Bravo pump were quite cheap... unlike the Honwave second seat! My twist on gauge came with the boat.
It seems from the Suzumar list the 2009-on stringer end caps are identical to my 2011 Honwave ones... so I wonder if you could assume the older Honwave was the same as the older Suzumar like yours? If so the old style Honwave ones might fit... worth checking with a Honda dealer.
Of course if you are lucky and Suzuki have the same parts supply/pricing as Honda a Suzuki outboard dealer might help??
The valves seem to be generic Halkey Roberts types - all are working fine and I have the pump adaptor but as you know wise to have a spare for the sake of a few quid - better than a ruined holiday etc!
I've got some of that thermo moldable plastic so might just try making a rough approximation of the cap for now.