Sherri, I don't know the answer to your question, but I suspect it MAY not have had the "Master Switch". I base my opinion on the manual for a 1990 HiLo that I found here: http://www.hilotrailerforum.com/f49/...-classic-2016/
(Post #1). It shows a "Raise/Lower" switch and a safety light that would be on if the safety bar is not engaged. I would think the raise/lower switch would be just inside the door, near the floor, based on the raising instructions in that manual. Possibly, someone with a 1991 HiLo that sees this may be able to give you a more detailed answer.
The "raise/lower" switch would be one that has 3 positions and is spring-loaded to the center, neutral (off) position. The upper position would be to raise the trailer and the lower would lower it. A hardware store, such as Ace Hardware should have a switch of this type and any switch that functions as I've described would be fine. You'd wire it using the schematic in the manual I've pointed you to.