There are several salvage yards in the US that might have a door handle with lock and key.
Here is a list of salvage yards...
RV Salvage Sources
I briefly looked thru some of the listings to see if they had any salvaged early 90's Holiday or Alumalite units and did not see one.
Bontragers apparently sells salvaged doors. You might email them and see if they can help. Also Visone's is a large salvage yard you might contact.
BONTRAGERS SURPLUS PARTS
18719 E US 12
White Pigeon, MI 49099
Phone: (866) 483-7017
Email:
surplus@myrural.com
Web:
www.bontragers.com
VISONE AUTO MART
243 Fields Ln.
East Bernstadt, KY 40729
Phone: 606-843-9889
Email:
ashley.visone@gmail.com
Web:
www.visonerv.com