I'm not clear about why cables are an issue. Do you need some for a repair, or just want to get a spare set (just in case) while they're still potentially available. Having a spare set is probably not necessary; with routine inspection and lubrication, correct operation, and common sense use (not storing your Hi-Lo, outside, in the raised position through snow season), the chance of a cable failure is REALLY small. Our 1969 Bon Voyage still uses the original cables, and I'm not noticing any significant wear.
Frankly, I've always lived so far from from the factory (and even a dealer) that I've naturally come to look locally (and successfully) for parts support. Always thought that if a cable failed I'd either go to Home Depot, buy the cable, and make it up myself... or go to our local rigging supply outfit and have them make one. There is nothing unique about cable from the Hi-Lo factory.
Regarding Trailmanor trailers, other than seeing them on the road, I don't know anything about them. This may be the wrong bulletin board for that kind of feedback.
1967 17' Hi-Lo Bon Voyage (1967-1969)
1969 19' Hi-Lo Bon Voyage (1969-2011)
2004 27' Hi-Lo TowLite (2010-present)
2015 Chevy Tahoe LTZ