The filter from the later B25/T25 is just a bit too long, the original was not mean't to be replaced but to be cleaned in petrol and reused. Of course they do need replacing eventually and I have managed to cram one of the later ones in by removing bits of it but would much prefer the proper filter. Vokes do not have it listed and emails are ignored but they did make some for the Daytona BSA rebuild done a few years ago so maybe Myles can give us some info.
Jon, Kommando- thanks for the replies. I acutally got one of the later B25/T25 filters when I got the E37, and realized it doesn't fit properly. I managed to soak and clean up the original element to the point not having any visible metal flecks, and bringing back the grey-felt color. If anyone needs that later B25/T25 filter element and seal, let me know and I'll drop it in the mail, as I have no use for it.