I'm actually going to try out their stock endpin - I can return it if it doesn't work (or use it as a model for something better before I return it), I've got some ideas up my sleeve but need to actually have the bass in my hands to work out what will work best.
in other news, someone in the US pointed me to a thing called a ninomute that makes EUBs sound way more acoustic-like, and wanted to sell me one for $50 plus shipping (and then VAT and the UK charging me £10 to collect that), so I took a good look at the thing in a couple of video reviews, and realised I can make my own for like 50p.
It's literally just a strip of compact foam with slices into it that fit over the strings, up against the bridge. Different thicknesses give more or less dampening, so you can have more or less "thump". I've got an old leather belt and some packing foam that'll do the trick fine, I can experiment with different thicknesses and then have a couple handy for different sounds.