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There's lots of options. I don't think it's any more unusual than other sizes. Remember what @svenhöek said though; some manufacturers call it 30.0mm instead of 29.8mm (or they actually provide a 30.0 and it compresses the extra 0.2mm).
I've had one from eBay on my pompino. IIRC it was branded Acor or similar (but don't quote me on that) and cost about a fiver. Worked fine.
Salsa lip lock is indeed a lovely clamp if you can get one.
Thanks. 29.8 what an oddish measurement... Does anyone have one lying around by any chance?