I’m sure this is an old one, but I have a friend looking for a  71 DT1 250 sealed headlight. I know there’s a conversion to use H4 with W clips but was wondering if somebody has found anything else. Thanks in advance.

Earliest DT1s, and other vehicles of that era, used headlights where the bulb (APF) could be replaced if it blew. All other mounting and beam adjustment fitments are the same as those for the sealed beam headlights. Just for your info (as I'm in the UK), this is one for a CT1 that I've got on fleabay - I might have a spare DT/RT one as well.

Yamaha rare early headlight CT1 CT2 CT3 RD125 RD200 US fitments 251-84120-61 | eBay UK

Alan, the CT headlight and rim should fit the DT1 of that era.  The main difference is the DT had a higher wattage bulb fitted (and wattage marked on the reflector).