You could try Simon Westley at Cranfield, I know he has repaired both engine frames and nose legs from PA38's in the past - if he can't, I suspect he might point you in the right direction. He is a CAA certified welder, which helps in the decision about repair or replace.
Simon Westley
Westley Aircraft Services
Cranfield
Bedfordshire
07752 241185
46 Partridge Piece
Cranfield
Beds
MK43 0BP
Tel (Daytime):
Tel (Evening): 01234 757977
Tel (Mobile): 07752 241185