I ended up getting a decent deal on this (admittedly rather worn, but fully functional)
Chips & Technologies Super EGA card, which seems to be a variant of
this card (chipset also described
here).
Looking forward to trying it out!
In addition to this, I got my hands on a shiny EGA Wonder 800+ card from a friendly domestic seller in a Facebook group:
For this nice-looking item, I paid the equivalent of £34 (including shipping), ie just slightly more than half of what I paid (£66.25, including shipping/VAT/customs) for the worn Super EGA card described in my previous post, which, alas, had already shipped by that point.
That's what I get for being too trigger happy, I suppose. Then again, it will be interesting to try both cards and compare them to one another!
I wonder, for example, if my PX-22 monitor will be able to properly display the 16 color VGA mode that the 800+ allows for.
Note that the card on the photo above seems to be almost identical to the 800+ card shown
here, apart from differing chip numbers in one or a couple of cases, so this purchase seems to be the brand-name deal and not some OEM/cheapster variation.