If you haven't run across a reference on the board yet, many HiLo parts are available from J&R in Ohio. The link below goes to an old thread announcing that they're there to support the HiLo community, and they're definitely still in business - I've purchased a number of parts from them as recently as a couple of months ago.
Don't be surprised if it takes them a bit of time to respond to e-mails - if my understanding is correct, there's just the two guys there, and they stay pretty busy.
https://www.hilotrailerforum.com/f5/...parts-com-893/