Crud.
I must be getting old. I forgot about the battery issue.

Oh well ... Maybe I can find one of those front axle mount odometers that click with every wheel revolution.

The classic mechanical speedo/odo won't work. All I can find are for 26" and larger, (trike has 24" wheels) and/or are set for Km per hour.
I don't do Km's or the metric system.