We have seen at least three different 12ga. DHE Repros with 30" barrels listed for sale right here on this site in the For Sale subforum. There is currently another one for sale; this part of an A-1 Special 2-bbl. set listed on GI:
https://www.gunsinternational.com/gu...n_id=101941476
A forum associate owns a 12-ga. DHE
Steel Shot Special and purchased a 30" barrel set separately and had that barrel set fitted to his gun. It's been guestimated that there were approximately 25 12ga. 30" barrel sets produced.