After a lot of research, I went uber-cheap.
https://cpc.farnell.com/citronic/casa-10ba/active-10-sub-300w-rms/dp/LS06176
I don't actually need 'capable' and I already own more high-quality PA kit than is good for a man; what I need is 'suitable for tiny playing areas, usually in venues with lousy acoustics' where all that matters is form factor and (above all) light weight.
I'd never take a Citronic 1x10 sub to a serious gig, given that I already own two 2x10 subs and a 1x15 sub, and more importantly most of my gigs have no need for a sub-woofer at all. But I always have a benchmark tiny pub in mind, the sort of place where there's nowhere near enough room for the band / there's a 5'7" ceiling / the bar is five feet in front of the band / the load-in is a complete nightmare. My benchmark used to be The Red Lion in Leighton Buzzard, then it was The White Hart in Chalfont St Peter, and now it's The Load Of Hay in Bushey Heath.
Places like this need tiny speakers for all sorts of reasons, so I can use my QSC CP8 monitor wedges as PA tops instead but obvs they really don't handle bass very well. A tiny, lightweight, lowish-quality sub is exactly what I need to re-balance the system. @Chienmortbb suggested the Wharfdale and I'm actually a fan of their stuff but it weighs 21Kg so is only marginally lighter than the 23Kg MarkAudio units I already have.
Where the Citronix scores is that it weighs just over 16Kg. Because of the handle placement it's still a 2-handed lift, but a very easy one. I can still manage the Mark Audio units but it's getting harder every year to lift those buggers into the back of the car and then manoevre them around. 🙄