Vaillant do/did one for ecomax boilers (Part number 2370104) which I imagine is still available although I couldn't find a picture. Or try googling "Vaillant 180985" which is the siphonic trap out of an ecoTEC plus. You could easily bodge that under any boiler.
You do have a better chance of the condensate not freezing if it's sluiced down in batches rather than comes as a continual drip. That's why boiler manufacturers put autosiphons in.
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